ring gapping and basic piston ring info YOULL NEED

[grumpyvette]

YES YOU NEED TO READ THRU THE LINKS THAT'S WHAT THEY ARE THERE FOR...AND THERE'S A GREAT DEAL OF USEFUL INFO IN THOSE LINKS



viewtopic.php?f=53&t=247

viewtopic.php?f=51&t=588&hilit=honing%E2%80%A6

http://www.bhjproducts.com/bhj_content/ ... pplist.php

viewtopic.php?f=53&t=1797

http://www.hastingsmfg.com/ServiceTips/ ... ishing.htm

http://www.enginebuildermag.com/Item/38 ... rings.aspx

viewtopic.php?f=69&t=3814&start=240


GET THE RING END GAP TOO TIGHT ,OR PISTON SIDE CLEARANCE TOO TIGHT,OR NOT PAY ATTENTION TO THE LUBE SYSTEM DETAILS,AND WHEN THE RINGS EXPAND WITH ENGINE HEAT THE ENDS TOUCH THE RINGS LOCK IN THE BORE AND THE PISTON LANDS SHEAR OFF, it RESULTS IN EXPENSIVE FAILURES GET THE GAP A BIT TOO LARGE AND YOU MIGHT BURN A BIT MORE OIL OR LOOSE SOME COMPRESSION, YOU'LL SEE A CHART LATER IN THE THREAD, BUT GENERALLY YOU'LL WANT .0045-.0065 PER INCH OF BORE DIAM. FOR A RING END GAP


HONE WITH HONE PLATES to duplicate the stress the head bolts place on the cylinder walls to get a true round bore wall surface






use of a deck plate allows the head bolts to be torqued ,this duplicates the stress the heads when installed exert on the block and allows a much better ring seal
BORING and HONING a blocks bore are best done at a local machine shop where clearances and surface finish are more accurately controlled, BUT, IF your going to be honing the bores for MOLY rings I,d suggest a 240-280 grit hone a 45 degree cross hatch angle and a constant flow of flushing liquid washing over the stones and bore surface to keep the stones from clogging with micro grit trash, that gets removed from the high points in the bore surface.
Ive used both a flush of 90% diesel fuel mixed with 10% marvel mystery oil, as a flush and Ive used hot water with a couple teaspoons of dawn dish washing soap, both work, but I think the hot water and dawn solution produced the most uniform result, on the bore surface but that requires a good deal of cleaning and washing the block just like the diesel fuel mix as you darn sure want to remove all traces of grit and prevent rust forming from moisture so after hone work I power wash the block with a pressure washer,, flush the surface with alcohol paint thinner as it tends to get under and lift out micro crud and speed surface dry time ,then I spray it over with WD40 and heat it with a heat gun to remove moisture traces then re-spray it with WD, 40 [/b]

washing the blocks surface with alcohol, and drying with high pressure air helps dry a lock after a pressure washing


http://www.harborfreight.com/1600-watt- ... 69342.html
http://www.circletrack.com/enginetech/c ... for_speed/
one factor I find amazing is how few guys realize that the rings MUST have space both above the ring and behind the ring in the piston grooves simply because its the hundreds of PSI of cylinder pressure that first forces the ring into the bottom of its groove then the pressure gets behind the ring and tends to expand it and hold it into the bore that is a huge factor in how effective the ring seals combustion pressure in the combustion chamber, if the clearances are filled with carbon build up the rings loose a great deal of there ability to seal.




ideally the pressure above the piston gets behind the top compression ring and increases the force holding the ring face to the bore surface, noticeably;y more than the ring tension alone can do.
http://www.sjdiscounttools.com/lis24000.html



measure carefully as the piston groove depth and back clearance must match the rings you use or youll have major problems


viewtopic.php?f=53&t=1797&p=4586#p4586

viewtopic.php?f=53&t=3897&p=26602&hilit=tool+groove+piston#p26602

viewtopic.php?f=53&t=509&p=632&hilit=tool+groove+piston#p632

viewtopic.php?f=53&t=9490&p=34908&hilit=ring+compressor#p34908

viewtopic.php?f=53&t=5454&p=16301&hilit=ring+back+space#p16301









yes thats a VERY commonly over looked factor, the chipping seeming to be sensitive to how aggressive I pushed the ring into the grinding wheel, and how agreasive the grit used is, the slightly higher cost diamond grit wheel IS worth the cost difference and how fast its spinning all effect results, even the direction the grinding disc spins effects the cut, it generally works best is the wheel , on the ring filer disc is rather smooth and the rings barely moved into the cutting disk with minimal resistance



BTW, most piston compression rings have a dot on the upper surface to indicate the side designed to face the top of the piston


yes as always theres cheap,functional, and theres expensive precision ring filers
http://www.abs-products.com/specialty-t ... nder.shtml

http://www.youtube.com/watch?v=RHSoSZvHoCo



Indycars posted these GREAT PICTURES OF HIS RINGS UNDER MAGNIFICATION SHOWING THE MICRO CHIPS IN THE MOLY RING FACING
http://www.speedwaymotors.com/Precision ... ,2915.html



NOTICE the two totally different OIL ring scraper ring widths in this picture above,OIL RINGS come in dozens of designs so, you can not use all oil rings on all pistons and you can,t swap expanders and wipe rings thru different designs, and you must verify piston groove measurements , measure carefully as the piston groove depth and back clearance must match the rings you use or youll have major problems
http://www.summitracing.com/parts/SUM-906795/

http://www.muller.net/sonny/crx/rings/index.html

http://www.teglerizer.com/triumphstuff/75w_newrings.htm

http://www.summitracing.com/parts/PRO-66785/

your going to need decent feeler gauges


if the ring gaps not correct your engine could easily get screwed up

here is where you, or your machine shop can screw things up on ring to bore seal,Don’t get crazy trying to get the minimum end gap.
if you have a minimum possible end gap for the piston rings, they will not provide a significantly better seal than the correct or slightly larger end gap, do not push it to minimum spec. the saying goes like this: if the gap is too big nobody will know, but if it is too small everybody will know, be cause if the end gaps too small the ring ends touch, lock the piston in the bore, shear off the ring lands and destroy the engine, a but to large results in not much but a tiny bit more oil being used

Often filing rings is required, so be sure to clean the filed area with sandpaper to smooth the burr then wash with soap and water. Little horsepower is lost through the increased gap and what good is horsepower if your rings come together and break a piston or two
when you hone the bores,get and use block deck hone plates, during the hone process , keep in kind you want to use the same (STUDS OR BOLTS) the machine shop used and the same torque settings they used when the cylinders were honed with deck plates or the distortion of the bore and ring seal won,t be identical (exactly round)or ideal , ring tension helps seal the bore on the intake stroke but on the power stroke cylinder pressure forces the rings hard against the lower ring land surface, the space above and behind the ring is nearly instantly filled with hundreds of psi of cylinder pressure forcing the ring out against the bore wall.
think about this a second,before spending your cash on gap less rings.that can cost 3 times what standard gap piston rings do,
With the engine temps up to operational levels the ring end gap is generally in the .007-.005 range and actual piston to bore side clearance is in the .001-.002 range, that's not counting a film of oil covering and filling much of that remaining clearance,and piston temps that can easily exceed 400f , now consider that at even just 3000rpm, theres 25 compression strokes per second, which are taking up 1/4 of that rotational time frame, so in effect, to get gas leakage past the rings you have to forced the compressed gases past two piston ring end gaps (FIRST AND SECOND COMPRESSION RINGS) located in a randomly staggered location, thru a pair of ring end gaps that are about .002 x.006, in less than 4% of a seconds time.
when they do those impressive leak down tests the piston and rings are stationary, not reciprocating at and changing between high cylinder pressure and several dozen inches of exhaust scavenging vacuum,25-60 times PER SECOND, like rings in a running engine, nor is the engine operating at anything close to operational temps and pressures
while theres zero doubt that the gap less rings in theory will seal a bit better,if properly installed, the real world advantages, are minimal during true operational conditions, because you can,t force much compressed gas forcing its way past the piston ,down thru a hole on a set of staggered ring gaps, over that very brief time frame, thru what is effectively the size of a hole in a needles eye.



watch this and read thru the linked info, posted below, there's only a few ways to screw up an engine rebuild faster than NOT having the rings installed correctly or gaped to match the application, and heat range.
run the ring gap too tight, and the ring ends touch and the ring can lock against the bore, frequently busting ring lands or pulling the top of the piston ring land clear off, resulting in,having chunks of busted piston ring land compressed into the quench area, or results in bent connecting rods and cracked cylinder heads, bent valves etc.

http://www.youtube.com/watch?v=moJB7lKd25U&NR=1



http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRO%2D66785&N=700+115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SME%2D906000W&N=700+115&autoview=sku

http://www.sswesco.com/ss/sssugges.htm

viewtopic.php?f=53&t=5454

http://www.babcox.com/editorial/us/us20114.htm

http://www.circletrack.com/enginetech/c ... index.html

http://www.kb-silvolite.com/article.php ... ad&A_id=56

http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

http://www.stockcarracing.com/techartic ... index.html

http://www.riken.co.jp/e/piston/b/b_1.html

http://www.carcraft.com/techarticles/pi ... index.html

http://www.aa1car.com/library/ar293.htm

http://www.gmhightechperformance.com/te ... ation.html

http://www.aa1car.com/library/2005/eb010550.htm

http://www.jepistons.com/dept/tech/dl/p ... rc4032.pdf



http://www.aa1car.com/library/ring_end_gap.htm

http://www.aa1car.com/library/ring_end_gap.htm
http://www.circletrack.com/howto/1818/index.html

http://www.chevyhiperformance.com/howto/0706ch_file_fitting_pistons/index.html

http://www.popularhotrodding.com/enginemasters/articles/hardcore/0604em_building_the_short_block/piston_rings.html

http://kb-silvolite.com/article.php?action=read&A_id=56

http://www.sswesco.com/ss/sspow.htm

http://www.racetep.com/totalsealframe.html

http://www.cdxetextbook.com/engines/com ... rings.html

http://www.dragracingaction.com/index.p ... press=3504

http://www.federalmogul.com/korihandboo ... ion_18.htm

http://kb-silvolite.com/article.php?action=read&A_id=32

http://moodle.student.cnwl.ac.uk/moodle ... rings.html

BTW I recommend THIS TYPE of piston ring compressor (below)as the type in the video can and occasionally does allow the rings to pop out and jam, or break far more frequently .

the picture lacks detail, but the interior of the compressors tapered, you tighten to a slide fit on the piston diam. and the rings compress fully as they are entering the cylinder entrance and only expand after entering the bore.

http://www.amazon.com/KD-Tools-850-Diam ... 0002STSMG/

this type (ABOVE) handles many applications but the cheap versions are a P.I.T.A. to work with



BTW when you go to buy a ring compressor....this type(ABOVE & BELOW) works far better than the others, but its specific to a very limited range in bore size applications



http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRO%2D66766&N=700+115&autoview=sku

Proform 66766 $31


how they work is you clamp it around your piston and adjust it to that size before the rings are installed so the piston is a snug slide thru fit, then, install the rings, dip the rings and piston in clean oil, place the compressor over the cylinder on the block with the base firmly held against the block deck and push the piston into its much larger open entrance, as it slides thru the funnel like construction squeezes the rings into the grooves and they can,t spring back out until they are in the bore, remember to line up the rod bolts and having them covered with the ends of a 3 ft long section or 3/8" fuel line to protect the crank journal is a good idea, having a ROD GUIDE TOOL you can use to guide and PULL THE PISTON INTO THE BORE WITH IS EVEN A BETTER IDEA

youll be surprised at how much easier they slide into the bore if you BOTH pull/guide and push the pistons into the cylinders rather than just beat them in with a hammer handle, it takes some practice but a few taps to get them moving with a fist, while pulling and guiding the rod into its journal is usually all that necessary with a well oiled piston and that type of ring compressor, btw IVE dunked my piston/ring assembly's in a can of MARVEL MYSTERY OIL just before installation with a ring compressor and have never seen the slightest indication of problems either on ring sealing getting the rings broken in, or on tearing the engines down later for inspections




if you have oil ring expanders with the plastic bits,they are there to prevent you from over lapping the ends of the oil ring expander, theres some oil ring expander s that are vertical ,some horizontal, but all have the ends butt , none over-lap

btw heres typical detonation damage, and in this case, resulting from a bit of nitrous, that boosted the pressure, but the results would be similar on a high compression engine subjected to crappy fuel and high loads at high rpms without nitrous, notice the sugary/frosted appearance and rounded edges of the melted areas



damage to the ring lands can be caused by detonation or just the ring gaps set too tightly, if the piston shows no frosted appearance its usually the ring gaps too small, or excessive heat, to lean a mix, to much ignition advance,etc.


most applications would have a ring gap of about .004-.005 per inch of bore diam.
but tests have shown even a .050 end gap has only a marginal effect on engine power or blow by, simply because at even 1000rpm theres slightly more than 8 power strokes per second, and the pressure is near max mostly in the 10 degrees before and 30 degrees after TDC, theres very little time to force much thru a .005 or less piston to bore clearance and two .050 end gaps even if that was the case

viewtopic.php?f=53&t=3897&p=10316#p10316

obviously if you've been around engine rebuilds, long enough, your aware that you'll eventually see guys installing rings in piston grooves by spiral twisting them into place, like the picture below depicts



the problem, with that method is that its not at all difficult to leave the piston ring twisted permanently, or warping it to the point it either breaks , or its bent ,degrading its ability to seal against the bore wall.
so its a good idea to carefully use a expander tool, but only expand the ring enough to install it.


http://www.summitracing.com/parts/shc-94662

[grumpyvette]

Ive had MIXED results , using gap less rings vs standard rings,
and Ive found the condition of the surface of the cylinder , the care taken during the assembly, the piston, design and the use of a hone with a deck plate , during the hone process and the grit used and angle of the hone job all effect the power results more than swapping from standard to gap less, rings, also keep in mind the brand and type of rings does effect results.


correctly honed cylinder walls allow the rings to seat against and to form a mated sliding surface, between the piston and the blocks bore with the rings, forming the flexible sealing surface, between the moving pistons and stationary bore walls, and remember the cylinder bore changes size and shape slightly ass it and the piston heats up.
To promote a good seal of the combustion chamber ,pressures from the combustion chamber on both the compression and power stroke , need to seal those pressures from reaching the crank case,and rotating assembly. the rings need cylinder pressure to get to exert force on their upper surface, and get behind them in the ring grooves to expand them outwards, the both the pattern of the scratches and the depth and consistency of the surface roughness cause the rings to be supported on a thin film of oil, preventing the bore from wearing excessively but allowing the rings to form a good seal. you'll need to use a torque plate to induce the same stress on the block the heads do when they are bolted on to the engine if you want the bores to be as round as possible during the honing process

IVE used them (total seal and other gap less rings)on several engines, as far as IM concerned they are NOT worth the extra cost, they work just fine but IVE seen little or no improvement over standard rings that were installed correctly.think about it, theres about 2-3 thousands at the most between a piston and a bore once the engines up to operating temp,the ring end gap is about 5-8 thousands at most once the engines up to operating temps, a pistons doing a compression stroke 20-60 times a SECOND when the engines running, how much compression can you loose thru the end gaps of two compression rings with their gaps spaced on different sections of the piston anyway.

ILL make this REALLY SIMPLE!
this type works far better than the others, its nearly impossible to tell from the pictures here but the inside diam. is tapered and the rings compress as the piston passes thru the ring compressor ring, and they work far easier than those sheet steel band with a radiator clamp style compressors like the one most guys started out with, yes they only work over a limited range in bore sizes say 4.00-4.200 then you'll need the next larger size, but Ive got 5 in my tool box and that covers 3.875"-4.650"




BLOCKS SHOULD BE HONED TO SIZE WITH TORQUE PLATE SIMULATING HEAD BOLTS STRESS ON THE BORE WALLS

BORING and HONING a blocks bore are best done at a local machine shop where clearances and surface finish are more accurately controlled, BUT, IF your going to be honing the bores for MOLY rings I,d suggest a 240-280 grit hone a 45 degree cross hatch angle and a constant flow of flushing liquid washing over the stones and bore surface to keep the stones from clogging with micro grit trash, that gets removed from the high points in the bore surface.
Ive used both a flush of 90% diesel fuel mixed with 10% marvel mystery oil, as a flush and Ive used hot water with a couple teaspoons of dawn dish washing soap, both work, but I think the hot water and dawn solution produced the most uniform result, on the bore surface but that requires a good deal of cleaning and washing the block just like the diesel fuel mix as you darn sure want to remove all traces of grit and prevent rust forming from moisture so after hone work I power wash the block with a pressure washer,, flush the surface with alcohol paint thinner as it tends to get under and lift out micro crud and speed surface dry time ,then I spray it over with WD40 and heat it with a heat gun to remove moisture traces then re-spray it with WD, 40



http://www.harborfreight.com/1600-watt- ... 69342.html
Fitting Piston Rings

Always ensure that you have sufficient ring gap.(usually .004 per inch of bore diam. MINIMUM) This is checked by using the piston skirt , or a short section of PVC pipe or a tool designed for the job to push the ring down into the lower unworn part of the bore, or about an inch down from the deck on a new honed bore,. Ring gap can be adjusted by filing the ends. make sure that the rings are free in the grooves without excessive up and down play. Gaps should be staggered around piston (120 degrees) with none facing directly to front or back When replacing rings, any markings should always face upwards. If there is a taper on the inside it should face upwards. Any taper on the outside should go down., rings tend to slowly rotate in the piston grooves, so don,t be shocked if the gaps don,t stay consistently spaced/separated during use.


[/b]

http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRO%2D66766&N=700+115&autoview=sku

http://store.summitracing.com/partdetai ... =pro-66766 (4.0-4.090)

http://www.kb-silvolite.com/news.php?ac ... ad&N_id=27

http://www.jepistons.com/dept/tech/dl/p ... rc2618.pdf

http://store.summitracing.com/egnsearch ... toview=sku (4.125-4.205)

http://store.summitracing.com/partdetai ... toview=sku (4.250-4.310)

http://www.jegs.com/i/JEGS/555/80516/10002/-1

http://www.racetep.com/totalsealframe.html

http://www.bikernet.com/garage/PageView ... ageID=1199

http://www.rosspistons.com/information/ ... lation.pdf

now years ago, we were instructed to leave the second ring gap at a tighter .004 per inch of bore with the upper top ring having the larger end gap due to the higher heat levels, it operates under ,well extensive testing in recent years shows that
(1)the second ring gap needs to be larger because if significant cylinder pressure builds between the top and lower ring the upper ring seal is quickly lost
(2)theres very little cylinder pressure lost thru the ring gaps in the thousandths of a second the rings are compressing the fuel/air mix, or during the power stroke, because most of the blow by, is the result of less than effective ring to cylinder wall seal
(3) ring seal is destroyed if the ring gap allows the rings to contact, or the rings butting destroys the piston lands
(4) ring gaps up to about .045 have very little effect on blow by or oil use

http://www.kb-silvolite.com/article.php ... ad&A_id=64
Application

Bore x
High-Performance Street / Strip
.0045”Top Ring
.0055”2nd Ring
Street-Moderate Turbo / Nitrous
.0050”Top Ring
.0055”2nd Ring
Late Model Stock
.0050”Top Ring
.0055”2nd Ring
Circle Track/Drag Race
.0055”Top Ring
.0060”2nd Ring
Blown Race Only
.0065”Top Ring
.0070”2nd Ring
Nitrous Race Only
.0070”Top Ring
.0075”2nd Ring




ball hones are fast and easy, to use but have the problem that they easily follow non[round cylinder surfaces, rather than tend to keep the cylinders surface flat and concentric like the bar hone design

[grumpyvette]

these threads have good related info, that you should read thru before starting the block prep, and rotating assembly process
Id point out that measuring the combustion chamber seal at TDC , during a leak-down test, has the obvious advantage of easily duplicating the test results giving you a base line to compare the cylinders from, yet I'd also point out that you'll occasionally find the rings and valves do function correctly at TDC but the bore walls are not consistent in size and shape thus as the piston descends down the bore the rings tend to loose seal. cracks in the lower cylinder and out of round bores can in theory pass a leak down test done at TDC. Id also point out that an operating engine has combustion chamber pressure and heat levels that far exceed the test pressure and the dynamic movement of the piston and ring to bore seal in an operational engine can be happening repeatedly ,from 450 to 4000 times a minute, and thats 8- 66 times a second at a peak pressure frequently exceeding 600 psi,and temps easily approaching 450F or more clearances are far tighter than on a cold engine, which means the very reduced time factor, and far tighter clearance significantly reduce the volume of trapped compressed gasses getting out of the combustion chamber so a static test at 80psi-120 psi while helpful won,t tell the full story.




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The Smooth Science of Cylinder Honing




BLOCKS SHOULD BE HONED TO SIZE WITH TORQUE PLATE SIMULATING HEAD BOLTS STRESS ON THE BORE WALLS
By Larry Carley

Larry Carley

The basics of honing cylinder blocks hasn’t changed much in recent years, but what has changed are the type of abrasives being used by many engine builders.

Silicon carbide and aluminum oxide honing stones of various grits have long been used in power honing machines and portable hones to finish cylinder bores. These types of abrasives are popular with engine builders because of their flexibility and low cost.

But in recent years, a growing number of performance engine builders and custom engine builders have started using the same type of honing stones that production engine rebuilders and OEMs use: diamond abrasives.

Conventional vitrified abrasives cut cleanly and do an excellent job of finishing cylinders – provided the right honing procedure is used to achieve a bore finish that meets OEM specs or the ring manufacturer’s requirements. But as the stones work the surface, they experience a lot of wear. In fact, the stones wear almost as much as the metal surface in the bore. Consequently, the honing machine operator has to constantly monitor the honing process and compensate for stone wear to keep the bores round and straight.

Tim Mera of Sunnen Products Co. in St. Louis, MO, says conventional abrasives require a balance between cutting action and stone life. As a rule, harder metals require softer stones. A softer stone requires less honing pressure, produces less heat and causes less bore distortion. So the bond that’s used in conventional abrasives is designed to wear quickly and expose the abrasives for good cutting action.

OEMs and production engine builders, on the other hand, don’t have the luxury of being able to baby-sit their honing equipment. Because of their higher production volumes, OEMs and PERs have to run their honing operations at higher speeds and with less operator supervision – which means diamond honing stones in most cases.

Diamond has long been the material of choice for high speed, high volume honing applications because of its excellent wear characteristics. Stone life depends on the hardness of the abrasive, the hardness of the substrate that holds the abrasives, the hardness of the engine block, honing speed, load and the amount of metal that’s removed. Diamond is the hardest natural substance known, so it can hold a cutting edge much longer than a conventional abrasive. This means the bond that holds the diamonds can also be harder because it doesn’t have to wear away as quickly to expose fresh stones on the surface.

Typically, a set of conventional vitrified honing stones might do up to 30 V8 blocks (240 to 260 cylinder bores) before they’re worn out and have to be replaced. A set of metal bond diamond honing stones, on the other hand, might do as many as 1500 V8 engine blocks (12,000 cylinder bores) before they have to be replaced. That’s a huge difference.

However, diamonds require a sizable up-front investment. A set of stones can cost $600 to $700 – which is a big jump from $15 to $35 for a set of conventional honing stones. Consequently, many small custom engine builders say diamonds are too expensive for their purposes. They also say they can’t afford to buy several sets of diamond stones to cover all the different bore sizes they do.

Even so, when the longer life of diamond stones is compared to that of conventional abrasives, diamonds may be more economical in the long run, even for a small shop (assuming an operator doesn’t overstroke a bore and break a stone!).

Pim van den Bergh of K-Line Industries, Holland, MI, says he sees more and more shops switching to diamond for a variety of reasons. "We were one of the first to offer diamond for honing machines because we saw its many advantages." He says it gives very consistent results with minimal stone wear.

Pros & Cons Of Diamonds
Because diamond is a harder material and wears more slowly than conventional abrasives, it cuts differently and requires more pressure. Diamond tends to plow through a metal surface rather than cut through it. This can generate heat and distortion in the cylinder bore if the wrong type of equipment, pressure settings or lubrication is used in the honing process. When done correctly, though, it can actually improve bore geometry by producing a rounder, straighter hole.

Diamond is also good for rough honing cylinders to oversize because it can remove a lot of metal fast. But finishing requires at least a two-step procedure. Otherwise, the surface will be too rough.

If you’re switching from conventional stones to diamond, you’ll generally have to use a higher grit to achieve the same Ra (roughness average) when finishing a cylinder. For example, if you have been using #220 grit conventional stones to finish cylinders for chrome rings, the equivalent diamond stones might be a #325 grit. If you have been using #280 grit conventional stones to hone for moly rings, the diamond equivalent might be #550 grit stones. The actual numbers will vary somewhat depending on the brand and grade of the stones.

A cylinder bore must have a certain amount of cross hatch and valley depth to retain oil. However, it must also provide a relatively flat surface area to support the piston rings. Ring manufacturers typically specify a surface finish of at least 28 to 35 Ra for chrome rings, and 16 to 25 Ra for moly faced rings. These numbers can be easily obtained with diamond stones and brushing, say those who use this honing technique.

One rebuilder we spoke to says he uses #325 grit diamond stones to end up with an Ra finish in the 20 to 25 range, which he feels is about right for moly rings. For some applications, though, he uses a #500 grit diamond to achieve a smoother finish in the 15 to 20 Ra range.

Final Finish
Something else that’s different when honing with diamond is what diamond does to the bore surface. Diamond tends to leave a lot of torn and folded metal on the surface, causing sort of a smeared appearance that doesn’t make a very good bore finish. Consequently, finishing the cylinder requires a second step to remove the damaged material.

One way to get rid of this material is to plateau the surface with a fine grit conventional abrasive (like a #400 or #600 grit stone). All that’s needed are a few strokes to shave off the tops of the peaks. But, the most popular method for finishing the bores when using diamond stones is to sweep the bores with a flexible brush or a nylon bristle plateau-honing tool. Brushing helps remove the torn and folded debris while improving the overall surface finish.

Chris Jensen of Goodson Tools & Supplies in Winona, MN, says, "there’s a lot of confusion about how to finish cylinder bores when using diamond. Since diamond leaves a lot of folded and torn metal on the surface, the bores need to be brushed to remove the debris. Many different names are given to the same tool and process. Some call it a plateau hone, a soft hone, a whisker hone or an ultra-fine hone. But they all do the same thing: they sweep across the surface to remove jagged peaks, folded and torn material."

Bristle style soft hones consist of mono-filament strands that are extrude-molded with a fine abrasive material embedded in the strands. The filaments can be mounted in different types of holders or brushes that can be used with portable or automatic honing equipment.

When finishing the cylinders with a brush, only light pressure is required. The rpm of the brush should be similar to that which the cylinder was originally honed, and no more than 16 to 18 strokes should be applied (some say 8 to 10 strokes are about right). Too many strokes with a brush may produce too smooth a finish that doesn’t hold oil.

Reversing the direction of rotation while brushing helps to remove the unwanted material on the surface. The end result should be a cylinder that provides immediate ring seal with little if any wear on the cylinder wall or rings when the engine is first started.

Sunnen’s Mera says, "brushing the bore after honing makes a huge improvement in the surface finish, whether diamonds or conventional honing stones were used to hone the bore. You can get the overall Ra down to 8 to 12, with RPK (relative peak height) numbers in the 5 to 15 range, and RVK (relative valley depth) numbers in the 15 to 30 range."

Equipment Requirements
Something else to keep in mind about diamond is that it works best in power honing equipment that has been designed to take maximum advantage of diamond’s honing properties. There are a number of companies that make diamond honing heads for use with various honing machines: Rottler, K-Line, Kwik-Way, Peterson, Winona Van Norman, Sunnen and others. But because of the increased loads, diamond may overtax some older power honing machines and increase the risk of stripped gears. It may be better to buy a new honing machine that has more horsepower and rigidity to handle diamonds.

"Most of our customers who hone with diamonds use a CK21 machine," says Sunnen’s Mera.

As for portable honing equipment, conventional abrasives are the better choice for this type of application. Most of those we spoke with say diamonds require too much pressure for portable honing equipment.

Another difference with diamond is the type of lubricant that’s required. A synthetic water-based lubricant is usually recommended instead of honing oil.

K-Line’s van den Bergh says, "water-based lubricants are easier and cheaper to dispose of than oil-based lubricants because they can be evaporated down to reduce their bulk. On the other hand, they occasionally require make-up water and have to be monitored to prevent bacterial growth.

"The type of lubricant you choose is very important because it can make quite a difference in honing performance. With conventional abrasives, you want a good quality honing oil. A lot of people run into honing problems because they’ve diluted their honing oil or tried to use something else like diesel oil or kerosene," says van den Bergh.

Anthony Usher of Rottler Mfg. in Kent, WA, says the OEMs all use long-lasting superabrasives with metal bonded honing stones. But the equipment and controls they use are very expensive, which makes it difficult to bring the same technology into a typical aftermarket job shop.

"About 12 years ago, we decided to change that. If new engines are originally honed with diamonds, why can’t we develop the same technology? So we set about developing honing equipment, controls and stones that would put the same technology into the hands of a job shop," says Usher.

"Diamonds last a long, long time. Because the stones don’t wear away, you can control the size of the bore more accurately," Usher explains. "This allowed us to build an automatic control system that allows us to size bores exactly the same every time."

Usher says for under $30,000, a job shop can buy a diamond honing machine that substantially reduces running costs and gives better results.

"The HP6A power stroking automatic honing machine is our newest product. It runs with diamond abrasives and has a programmable load control for both rough honing and finish honing. When it is finishing the cylinder, it automatically reduces the load because some cylinders have very thin areas that may distort if the load isn’t changed. The HP6A has a base price of $23,900 and a fully equipped unit goes for $28,000 to $35,000."

Plateau Finish Is Best
Regardless of what type of honing equipment or abrasives are used to finish cylinder bores, more and more shops are finding a plateau finish provides the ultimate finish.

A plateau finish is one that closely resembles a broken-in cylinder bore. When the bore is honed, the surface of the metal will have microscopic peaks and valleys. Peaks don’t provide much ring support, so as soon as the engine is started the piston rings start to scrub up and down and shear off the tallest peaks. As the engine continues to run, the peaks will be gradually shaved down until the cylinder bores are relatively smooth and flat (except for the valleys in the crosshatch that must be there to hold oil).

The normal engine break-in procedure will eventually produce a plateau finish anyway. But until it does, the rings and cylinders will experience unnecessary wear and the engine will experience increased blowby, oil consumption and emissions until the rings have seated – which might take several hundred or even several thousand miles to complete.

A better approach is to precondition the bore surface so the rings don’t have to "hone" the cylinders. A plateau finish will provide maximum compression right from the start, and eliminate most ring seating and sealing problems.

One recipe for achieving a plateau finish is to bore or hone to within .003˝ of final size. Then finish to final dimensions with a #220 or #280 grit conventional abrasive and follow up with half a dozen strokes of a #600 grit stone, cork, or a flexible brush or nylon bristle plateau honing tool.

If diamond stones are used, bore or rough hone to within .005˝ of final size. Then hone the cylinder to final dimensions with #325 to #500 grit diamonds, followed by six to eight strokes with a flexible brush or plateau honing tool. Many experts recommend leaving a little extra metal in the bore for final finishing if diamonds have been used to rough hone the cylinder. This is because rough honing with diamond leaves a very rough finish (over 100 RA depending on the grit of stone used).

Honing Hard Materials
In recent years, Nikasil coatings have provided a challenge for engine builders. Nikasil is a hard coating of nickel and silicon carbide about .0025˝ to .003˝ thick that is applied to cylinder bores to improve wear resistance. Invented by the German firm Mahle, Nikasil was originally developed for the Mercedes Wankel rotary engine. It has been used by BMW and Porsche in some of their engines, and is also used in many chain saw engines, some motorcycle and marine engines, and even many NASCAR Winston Cup engines.

Goodson’s Jensen says PERs have had success honing Nikasil treated cylinders with diamond. But for smaller shops that have only portable honing equipment, you can’t exert enough pressure with diamond to hone Nikasil. The best advice here is to use #220 silicone carbine and just do a couple of strokes to deglaze the cylinder. If a cylinder has to be bored to oversize, cut it out with a boring bar and then hone in the usual manner to achieve the desired dimensions and finish.

Ed Kiebler of Winona Van Norman in Wichita, KS, says new harder coatings on cylinder walls are forcing shops to change to diamond honing and to upgrade their equipment.

"I see a lot of shops who are interested in diamond but who don’t fully realize what’s involved in the diamond honing process. Diamond takes a lot of pressure to cut. Some people use diamond on portable hones, but realistically you can’t get enough pressure to make the diamonds perform well. Having said that, I truly believe the new harder cylinder coating materials are going to force people to go to diamonds," says Kiebler.

"The two-cycle stuff is all Nikasil. Now the outboard engines are going to Nikasil, too. All the NASCAR Winston Cup shops are using Nikasil cylinders. If it’s good for NASCAR, it’s not going to be long before you start seeing it in OEM engines," Kiebler explains. "The time is coming when you’re going to have to use diamonds if you’re going to hone Nikasil cylinders."

Kiebler says all most shops do is slightly roughen Nikasil cylinders. "You don’t really remove much material. The Winston Cup shops are running some of these motors five races before they redo the cylinders. The Nikasil coating really extends ring life and cuts down on ring wear."

OEM TRENDS
Dave Riley of Gehring L.P. in Farmington Hills, MI, a supplier of honing equipment to original equipment manufacturers, says almost all OEM internal combustion gasoline engines in North America today are being rough honed with diamond abrasives.

Riley says the OEM focus is on using water soluble synthetic honing coolants, which means diamond abrasives because vitrified conventional abrasives require honing oil. The other industry trend he sees is that cylinder bores are being respecified to smoother finishes.

"We’re talking 0.15 to 0.3 Ra finishes that are extremely smooth," says Riley. "They’re doing this to further reduce emissions. A lot of this is being driven by ring technology because rings can now survive in conditions that provide much less oil. However, in my opinion these new surface finish specifications are reaching the limits of technology."

One of the things that the OEMs do to achieve high quality bore finishes is to use computer numerically controlled (CNC) honing machines. The cutting speeds of these machines are 50 to 75 percent faster than what was used 10 years ago. Faster cutting speeds allows the abrasives to cut smoother, and finer abrasives can be used for a smoother finish without sacrificing cycle time.

Riley says there’s a dramatic difference in the amount of time the OEMs allow to hone a cylinder versus what a typical aftermarket engine builder or production engine rebuilder spends on the same process. He says OEMs typically spend only about 15 to 20 seconds to hone a bore with automated honing equipment. By comparison, it can take up to several minutes to manually hone a bore using a power honing machine.

"The OEM machines are completely automated and automatically control bore size and shape. They also measure and inspect 100 percent of the bores, and can sort by bore size if they run bore grades," he says.

"As the need to reproduce OEM finishes in the aftermarket grows, so too will the demand for honing equipment that can meet these specifications. This will obviously have an impact on honing costs," Riley explains. "We are developing a low cost, CNC-controlled single spindle honing machine for the aftermarket. The operator would load the block and the machine would automatically hone the bores to OEM tolerances."

Riley says Gehring also offers custom honing services for low volume engine prototype development and performance engines.

Cylinder bore quality plays a huge role in reducing friction and blowby for improved engine performance and durability. Better bore geometry also contributes to better sealing and more usable power. Riley says a lot of performance engine builders are hot honing their blocks to more accurately simulate actual running conditions. They also use torque plates when honing (some with simulated manifolds to further stress the block), and may even bolt a bellhousing to the block to reproduce the stresses and loads the block will experience in a vehicle.

"For OEM production applications, we have developed clamping and other methods to stress the block while it is being honed," says Riley. This is done to further improve bore geometry and sealing.

Aluminum Engines Soon
Riley says another OEM trend is the development of future engines that use various types of bore surface coatings in aluminum blocks. The coatings are sprayed-on powder metal or steel wire alloys that create the surface characteristics of a traditional iron bore.

"Last year, about 15 percent of the prototype engines we saw had some type of coated aluminum bores. This year, the percentage is up to 67 percent. So there has been a dramatic shift toward aluminum blocks with coated bores."

Coated aluminum bores have a number of advantages, one of which is better thermal conductivity between the cylinders and water jacket. Another is less heat distortion for better sealing. The coating provides wear resistance and allows the use of larger bores within a given block size for more total displacement.

Riley says the OEMs are currently acid etching the bores to finish them. But acid is environmentally unfriendly so the OEMs are developing alternative ways to finish coated aluminum bores that do not require acid etching. Diamond honing is used for roughing, but the finishing step is being done with nonmetallic bonded abrasives such as vitrified abrasives, rubber or brushes. The goal is to come up with a process that will work using water-based honing fluid.

How will the aftermarket refinish coated bores in aluminum engines? Riley says the most likely approach will be to hone away the original bore finish, then reapply the surface coating and refinish it back to OEM specifications.

Laser Structuring
A number of years ago, Gehring developed a unique process called "laser structuring" to enhance engine durability. The process uses a laser to burn small pits into areas of the cylinder bore surface where ring loading and wear are highest. The pits improve oil retention and ring lubrication, and significantly reduces ring and bore wear.

Riley says the new laser structuring process is now being used in Europe on diesel engines. "At 150,000 kilometers, the bores are showing almost no measurable wear (only 1 to 2 microns) and the emissions performance is the same as new," he says.

Riley says the laser structuring process can be used to create almost any kind of pattern imaginable in the bore surface. Typically, a series of dots or dashes 25 to 60 microns deep and 40 microns wide are burned into the top third of the cylinder by the laser after the bore has been semi-finished. A final honing step is then done using fine stones to remove any buildup of material around the pits and to finish the bore.

The laser part of the process takes about 9 to 15 seconds per cylinder and uses a special machine that rotates and lowers the laser beam as it is projected onto the surface of each cylinder.

Riley says the laser structuring process is ideal for hard blocks or those with special surface coatings that make them difficult to finish with conventional honing techniques. "It’s a perfect application for high performance, diesel and aircraft engines," he says.

Remember To Clean The Bores
As we wrap up this article on honing abrasives, one final point to remember is the importance of cleaning the bores after honing. Honing leaves a lot of metallic and abrasive debris in the bores – which must be removed before the engine is assembled. Washing and scrubbing with warm soapy water will remove most of the loose debris. Some engine builders follow up by wiping out the cylinders with automatic transmission fluid. The point is get the cylinders clean so there are no contaminants to damage the rings or to get into the oil.



<<Side Bar>>

WHY DIAMONDS ARE SO EXPENSIVE
If you’ve balked at the high cost of diamond honing stones, here’s a brief explanation why they’re so expensive:

Diamond is a special form of carbon that is formed naturally under extreme heat and pressure deep inside the earth. As such, it isn’t very plentiful or easy to find. Subsequently, man-made synthetic diamonds are mostly used for industrial abrasives.

Scientists realized that if they could duplicate the heat and pressure that formed natural diamonds deep in the earth, they could transform ordinary graphite (another form of carbon) into diamond. They estimated it would require temperatures in excess of 6,300 degrees F and pressures of approximately one million pounds per square inch to make the transformation occur. But as the scientists discovered, it wasn’t so easy. Try as they might, they couldn’t get graphite to change its crystal structure and become diamond – until General Electric researchers discovered the secret in 1951.

A catalyst was needed to make the change happen. The catalyst turned out to be a mixture of molten iron, nickel and cobalt. The various proportions of ingredients in the catalyst are still a closely guarded secret, so only a couple of companies in the entire world have the expertise to produce synthetic diamonds. In the U.S., synthetic diamonds are produced at GE’s plant in Worthington, Ohio. Several years ago, we were given a plant tour – but nobody except a trusted few are allowed to see inside the room where the diamonds are actually made.

GE says they can create different types and sizes of synthetic diamond for various industrial purposes by varying the temperature, pressure and type of catalyst. Man-made diamonds typically have a yellowish tinge and are as small as grains of sand. Even so, they’re ideally suited for their intended use as an abrasive. They’re just as hard as natural diamonds and actually perform better because of their custom-tailored shapes and characteristics.

[grumpyvette]

this info should help

How Piston Rings Affect Horsepower


Engine builders have to consider many variables when planning and assembling a performance engine. The piston rings are no exception, as mistakes here can cost you horsepower.

By Larry Carley

Larry Carley

The rings seal the pistons to prevent air and oil from being drawn past the rings into the combustion chamber during the intake stroke. During the compression stroke, the rings make sure the air/fuel stays in the combustion chamber and is fully compressed before it is ignited. During the power stroke, the rings prevent pressure from blowing past the pistons as the burning gases shove the piston down. And during the exhaust stroke, the rings make sure all of the spent gases are pushed out of the exhaust port.

Rings that do not seal well during all four phases of the four-cycle combustion process can reduce an engine’s power potential by 20, 30, 40 or more horsepower depending on the engine’s displacement, compression ratio and speed.

Rings that leak during the intake stroke will reduce air velocity and volumetric efficiency. Less air and fuel in the cylinder means less power. Rings that leak during the compression stroke will allow some of the air/fuel mixture to escape into the crankcase. Besides reducing compression and power, the unburned fuel that gets into the crankcase will dilute the oil. This will reduce the oil’s lubrication qualities while increasing the risk of engine-damaging sludge if the oil isn’t changed often.

Rings that leak during the power stroke will allow a loss of pressure that would otherwise be used to shove the piston down. The resulting blowby will also allow soot and moisture to enter the crankcase to further degrade the oil.

Finally, rings that leak during the exhaust stroke will reduce scavenging efficiency, allowing residual exhaust that remains in the cylinder to displace air and fuel during the next intake stroke. Again, more lost power potential. Blowby during the exhaust stroke will also allow more soot and moisture to enter the crankcase. If the engine has a turbocharger that depends on exhaust velocity for intake boost, ring leakage during the exhaust stroke can reduce exhaust flow, which reduces boost and power.

Another factor to consider is the amount of friction created by the rings against the walls of the cylinders as the pistons reciprocate up and down. Ring friction eats up more horsepower than the cam and lifters, the cam drive, the rocker arms or the crankshaft. Of the three rings in a typical ring pack, the oil ring accounts for 60 to 70 percent of the total friction created by the rings. Reducing ring friction by using smaller, thinner low tension rings can allow you to “find” horsepower that was previously lost. Low tension rings reduce friction and allow an engine to produce more usable horsepower.

However, dyno testing has shown that it is possible to reduce static tension on the top ring too much, causing a loss of pumping efficiency (vacuum) on the intake stroke. If you don’t get all the air/fuel mixture you can into the cylinder on the intake stroke, it’s not there to make power during the power stroke.

Optimizing Ring Sealing
The rings have to work with the pistons to provide the best possible seal. The rings prevent blowby by sealing against the groove in the piston, and against the cylinder wall. So to optimize sealing, the rings should be as flat as possible, fit the piston grooves as tightly as possible, have the least amount of end gap that the engine can safely tolerate, and be as conformable as possible to seal against the cylinder wall.

In late model original equipment stock engines, the rings are often moved closer to the top of the piston to eliminate the crevice where unburned fuel can be trapped. This is done for emission purposes and to help fuel economy. In a performance engine, the same logic applies. The more efficient the combustion process, the more power the engine will produce. But power also produces heat – a LOT of heat in a performance engine. This can be murder on both the top ring and piston groove if the materials are not able to handle the heat. For performance applications, you want a top ring made of ductile iron or steel. Wear resistant side coatings such as PVD or nitriding can help the rings survive this harsh environment. The top groove in the piston may be anodized or coated to minimize micro-welding and wear.

Scott Gabrielson of Federal-Mogul says one way to improve ring sealing is to modify the profile of the ring grooves so they provide optimum support for the rings when the pistons get hot. He says their Sealed Power DDP pistons feature an exclusive “Thermal Arching Compensation” (TAC) technology that creates a slight upward tilt to the ring grooves. This reduces blowby and improves oil control.

Gabrielson says it is important for engine builders to make sure the rings match the pistons they are using. “If you buy rings from one supplier and pistons from another, there is always a chance of a mismatch. The piston grooves may be too shallow or too deep for the rings resulting in improper backspacing. Or the piston grooves may not provide the correct side clearance for the rings. Federal-Mogul offers piston and ring sets that are perfectly matched to provide the best possible seal.”

Gabrielson says the conformability of the rings increases exponentially as the thickness of the rings is decreased. If you reduce ring thickness by half, conformability goes up 8X. Plus, the reduced tension reduces frictional losses.

“Years ago, most standard oil rings generated about 21.5 lbs. of tension. Today’s thinner rings, by comparison, are down about 7 to 8 lbs., or about one third of what they used to be.”

Bore Finish
Regardless of how much tension the rings generate, the best possible seal is going to be obtained with a round, straight cylinder bore. Gabrielson says a plateau finish is always best. “If you don’t plateau the finish, it will take longer to break-in and seat the rings. The scrubbing will eventually create a plateau finish anyway, so why not do it from the start?”

Cylinder bore distortion can have a negative impact on sealing, so to minimize distortion, Gabrielson recommends honing with torque plates (hot honing is even better!). Always use a new head gasket, and make sure the head bolts are tightened to the same value as when the cylinder head is installed.

Jeff Guenther of Hastings Piston Rings offers some suggestions for achieving a proper plateau finish. You should be using a profilometer to measure the various attributes of the surface finish. There are a lot of parameters you can measure, but these three are key:

Rpk = Peak Height
Rk = Core Roughness Depth
Rvk = Valley Depth

“A normal plateau finish with Rpk 8 to 12 microinch, Rk 25-35 microinch, Rvk 40 to 50 microinch) is a good starting point for general use. But for a performance application, an optimized finish would have the following parameters: Rpk less than 12 microinches, Rk 20 microinches, and Rvk of 40 microinches. If the application is something like a Pro-Stock or NASCAR engine, where minimum friction is a higher priority than longevity, you would want a smoother plateau with Rpk 3 to 5 microinches, Rk 12 to 18 microinches, and Rvk of 20 to 25 microinches,” says Guenther.

Ed Kiebler of Rottler provided the following suggestions as to how you can achieve an optimized surface finish in hard blocks or sleeves for Pro-Stock, Comp Eliminator, NASCAR or similar engines with a Rottler HP6A machine:

Hone the bores to size with 270/325 metal bond diamond stones (Rottler part number 514-9-14J) and Rottler water based coolant (p/n 514-4-71C). Hone at 170 rpm and 56 spm with a 35 percent roughing load. Then set the machine to plateau mode with a 20 percent load for four strokes with 600 grit metal bond diamond stone (p/n 514-9-14G). Keep the machine in plateau mode and change the stroke count to six strokes with 20 percent load. Use special diamond stones in flexible (red) bond (p/n 514-9-18P). The final step is to plateau for six strokes at 20 percent load using plateau brushes (p/n 514-9-14H). This process will produce a finish with Rpk of 4 to 6 microinches, Rk 18 to 22 microinches, and Rvk of 28 to 32 microinches.

Ring Selection
Bill McKnight of Mahle says ring selection plays a major role in optimizing horsepower. “In a maximum effort naturally aspirated engine, you should use the lightest weight and lowest drag ring pack available. In a power adder application, you also need to think about ring materials that can handle increased cylinder pressures and the extreme heat produced by nitrous oxide, superchargers and turbochargers.”

McKnight says a supercharged nitro methane drag race motor can bend a 2.0 mm wide top compression rings right out of the piston groove in less than four seconds! By comparison, a maximum effort naturally aspirated motor of the same displacement can usually get along just fine with a 1.0 mm wide (or thinner) top ring. He says engine builders need to carefully consider all the aspects of the ring pack, including ring width, radial wall thickness, the base material, the facing material, ring tension and rind end gap when choosing rings for a particular motor.

McKnight says that reducing the ring-to-piston vertical and groove back clearances can aid in reducing cylinder pressure loss. But he warns it is possible to go too far. “The top compression ring needs combustion pressure behind it to hold it out against the cylinder wall during the high pressure portion of the combustion cycle.

Conventional pistons rely on a calculated amount of side clearance to provide a path for combustion pressures to get behind the ring, energize it, and push it out against the cylinder wall. Unless some method, like gas porting, is utilized to route those high pressure gases to the back of the ring, overly tight side clearances can restrict that gas flow and de-stabilize the sealing process.”

McKnight says there’s a performance advantage if you can assure the piston ring sealing surfaces and piston groove sealing surfaces are flat and true. Any variation in either will allow the cylinder pressure to escape, negatively affecting the gains made by minimizing ring-to-piston groove clearances. He says that optimizing groove fit is well worth the effort in maximum effort naturally aspirated engines.

Gas ported pistons (vertical or lateral) also help with ring sealing. The ports provide a more direct path for cylinder pressure to get behind the top ring. Gas pressure helps force the ring out against the cylinder wall. In high rpm applications, gas porting helps thinner, lighter rings be more stable, reducing the tendency to bounce or flutter in the ring groove (which can break the seal).

End Gaps
McKnight says the optimal end gap for a top compression ring is when you achieve the smallest gap without butting the ends of the ring together when the rings get hot. “A good starting point for the top compression ring is .0045˝ per inch of bore diameter for a naturally aspirated engine, and .006˝ for a power adder application.

“The second ring end gap should be .005˝ to .010˝ wider than the top ring gap to prevent gas build up between the top and second rings. This can cause the top ring to flutter or bounce and lose its seal.”

In a heavily boosted or nitrous oxide application, McKnight says the second ring is forced more and more to act like a compression ring. Because of this, he says it should probably be gapped nearly the same as the top ring.

Piston ring manufacturers publish end gap recommendations in their catalogs and on their websites. Always refer to these recommendations as they will vary from one manufacturer to another depending on the type of rings used, what the rings are made of, and the application.

As a rule, the higher the power output of the application, the more end gap you should allow for thermal expansion.

In Federal-Mogul’s Speed Pro Piston Rings Catalog, for example, the end gas recommendation for a typical four-inch bore might range from .018˝ to .020˝ for a drag racing or oval track engine, to as much as .024˝ to .026˝ for a supercharged engine.

Many second compression rings today are a napier style that helps scrape oil off the cylinder wall. Jack Bishop of NPR says napier rings create a vacuum between the rings, so it’s a good idea to open up the gap on the second ring. He recommends the second ring end gap be 0.2 to 0.25 mm larger than the top ring end gap.

Bishop also notes that the thermal expansion rate of steel rings is less than that of cast iron rings. Consequently, you can generally run somewhat tighter end gaps with steel rings than cast iron rings.

Gapless Rings
The issue of where to set piston ring end gaps is moot if you are using a gapless style top piston ring. Bobby Chessman of Total Seal says 90 percent of Pro-Stock drag racers are using his rings because of the advantages a gapless ring offers: namely, a reduction in leakdown of 10 to 20 percent over a conventional style piston ring. “As a rule, people who run a gapless top piston ring see 3 to 5 percent more horsepower. That’s as much as 40 horsepower on a big inch motor.”

Chessman says Total Seal also makes conventional rings, too. But the gapless design is a patented feature nobody else offers. “An engine builder can use a gapless ring for either the top or second ring,” says Chessman.

Installation Tips
Insert the rings into a bore and measure the end gap with a feeler gauge. Adjust the gap as needed by filing only one side of the gap. Keep the gap as square as possible. This will allow the rings to run with the smallest possible gap.

Always use a ring expander so you don’t twist or deform the rings when mounting them on the pistons. Make sure the rings are installed with the correct side facing up (top is usually marked with a small dot). Also, stagger the location of the end gaps on all three rings 180 degrees apart.

Make certain the cylinder bores are clean before you install the pistons and rings in the block. Use hot soapy water, scrub brush and plenty of elbow grease to thoroughly clean the bores. Wipe with a clean white rag to check for any residue, then lightly oil prior to assembly.

Make sure the ring compressor is properly tightened so the rings don’t catch on the edge of the cylinder as the piston is being pushed into the bore.

For engine break-in, use a conventional oil or specific oil designed for breaking in engines. Then switch to a synthetic after 2,500 to 3,000 miles if you want the advantages of a synthetic motor oil.


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[grumpyvette]

UNDERSTANDING WHAT RING END GAP REALLY MEANS


At KB Pistons we get a lot of questions concerning ring end gap. This article will help put in perspective what ring end gap really means to an engine's performance.

First, what is ring end gap? It is the distance between the ends of a piston ring when it is compressed to cylinder size as in Fig. 1. The gap permits installation and allows for expansion and contracting with changes in temperature and cylinder diameter.

Fig. 1



Effect of Increased End Clearance on Oil Control
Maximum end clearance can be several times the recommended minimum with no measurable difference in oil control or ring life. The results shown in Fig. 2 are typical of the numerous fleet laboratory tests conducted to determine the effect of increased gap on engine performance.The rings used during the first test in the engine had .015” gap. Then the ends of identical rings were filed until the gaps were .085” and these rings were installed in the engine. As you can see, oil economy remained almost constant even when the gap was increased by .070”. When rings are installed in cylinders .010” larger than ring size, gap is increased by only .081”.

Fig. 2

Why Increased Gap Has Little Effect on Oil Control
The reason increased gap has little effect on oil control is because the portion of the gap where leakage can occur is so small. The portion of the ring gap that is not sealed is that which projects beyond the piston land. This unsealed area of the gap is circled in Fig. 3. The rest of the gap is sealed within the groove. Only about 1/10 of the total ring gap is not sealed within the ring groove.

Fig. 3


Fig. 4 compares the unsealed gap area of a standard ring in a standard cylinder on the left to that of a standard ring in a .010” oversize cylinder on the right. The arrow points to the unsealed gap. The difference in unsealed gap is very small. Depending upon the amount of ring land setback, the difference is approximately .00035” of a square inch or approximately one-tenth the area of a common pin head. In terms of oil control, this difference in unsealed gap area is insignificant.

Fig. 4

When a standard ring is installed in a standard of .010” oversize cylinder as illustrated at left in Fig. 5, the ring face contacts the cylinder wall around its entire circumference. However, when a standard ring is installed in a .020” oversize cylinder, contact between the ring face and cylinder wall is broken near the gap as illustrated at right in Fig 5. This would allow excessive oil consumption and blow-by. Therefore, rings cannot be used successfully in cylinders .020” larger than ring diameter. We would suggest using the proper ring size whenever possible (.030" piston with .030" rings). In some cases, however, you may be up against a deadline and this gives you a guideline to follow when you cannot attain the exact ring set.


piston rings move both in and out of the piston grooves and rotate as the piston moves thru its 360 degree rotation, keep in mind its the ring groove SPACING, and gap indexing and relationship to the rings, that is designed to minimize the loss of cylinder pressure thru the ring gaps, thats key, here, not where the gaps are exactly located , because the fact is that piston rings do tend to rotate in the piston groves in most engines, and its rare to find the ring gaps in the same location once the engines been run for several hours. Id also point out that failure to have the bore honed with the correct deck plates tends to reduce the ring seal. in fact having the rings rotate in the piston grooves tends to reduce bore wear, and keep the grooves clearance free from carbon build up




BTW GAPLESS PISTON RINGS HAVE TWO PIECES THAT EACH MUST BE GAPPED< THE IDEA IS THAT THE TWO GAPS IN THE SET ARE ON OPPOSITE SIDES OF THE PISTON GROOVE
IVE used the TOTAL SEAL GAPLESS RINGS in a few engines Ive yet to see any huge improvement over standard rings in either durability or power produced
READ THESE LINKS and sub linked info

viewtopic.php?f=53&t=5454&p=16301&hilit=groove+rings#p16301

viewtopic.php?f=53&t=4602&p=12273&hilit=piston+rings#p12273

viewtopic.php?f=53&t=4630&p=12416&hilit=piston+rings#p12416

viewtopic.php?f=53&t=110&p=3631&hilit=hone+plate#p3631

viewtopic.php?f=53&t=3897&p=17251&hilit=piston+rings#p17251

viewtopic.php?f=51&t=976

your going to need decent feeler gauges




worthless P.I.T.A. to use


GOOD and VERSITILE



WORKS GREAT BUT LIMITED TO A NARROW BORE RANGE AND EXPENSIVE

you generally only need to grind the tips of the expander ring (RARELY NEEDED OR DONE) or bend them only a tiny bit (PREFERRED METHOD)





if at all, in most cases they come out of the packager ready to install (THERE ARE EXCEPTIONS) the expander ring should sit level in the bore , and sitting parallel with the deck with minimal tension, their job is mostly maintaining consistent space between the wiper rings, which generally use a .018 gap and allowing oil to drain back thru the groove drain slots in the piston, its the oil scraper rings not the expander that provide much of the MINIMAL tension required to keep the oil ring in contact with the bore surface
as always a call to the manufacturer is a good idea, if you have questions because different ring designs require different clearances








http://www.hastingsmfg.com/ContentData. ... ntentid=65

http://www.hastingsmfg.com/ServiceTips/ ... depths.htm

http://www.youtube.com/watch?v=slS8CUHRNkc

http://www.chevyhiperformance.com/tech/ ... index.html

http://www.enginebuildermag.com/Article ... rings.aspx

http://www.enginebuildermag.com/Article ... mance.aspx

http://www.hotrod.com/techarticles/engi ... ewall.html

http://www.kb-silvolite.com/assets/auto ... ctions.pdf

http://www.superchevy.com/technical/eng ... ewall.html







[b]INDYCARS POSTED THESE GREAT PHOTOS[/b]
I talked with Eric at Mahle Motorsports yesterday to find out how the expander ring is suppose to work and how can I tell if the dimensions are correct.

According to Eric, there is no good way to measure this, but it should overlap about a 1/2 link when placed inside the cylinder. It's suppose to be bigger than the cylinder bore in it's free state. When you put the 2 oil rails plus the expander in the piston groove and then compress the oil rails it will compress the expander, making it's diameter smaller such that it does NOT contact the bore.

This is where very careful observation of these components is critical. The two oil rails MUST contact the shoulder on the expander. The expander ENDS must NOT overlap, rather the two ends must butt-up against each other or the oil rails will NOT do their job because they will lack the force needed against the cylinder wall to seal properly and control the oil. Don't get this right and your motor is going to smoke badly.

[grumpyvette]

read thru these related threads, posted below, youll find a good deal of info, on installing pistons and rings.

viewtopic.php?f=53&t=5454

viewtopic.php?f=53&t=4630

viewtopic.php?f=53&t=2795

viewtopic.php?f=53&t=2837

viewtopic.php?f=53&t=852

viewtopic.php?f=53&t=3897

viewtopic.php?f=51&t=588&p=869&hilit=hone+plate#p869

[87vette81big]

Is there anyone making Cylinder Block Torque Plates for a Pontiac V8 besides BHJ Grumpy ?
Need to purchase one for myself.
Last I checked they were around $575.00.
Sbc & BBC Torque plates in most shops.
Have a good engine machinist longtime friend I trust.
Watch him work start to finish.Even at 3-4 am just him & me.
Otherwise there are a few guys in Chitown.
Never know there . .
just 5.0 guys & me are close buds.

You ever make your own Cylinder torque plates ?
Can it be 1-2 inch thick Cold Rolled steel blanchard ground ?
How thick ?inches difference only on a Pintiac V8.
Or use cast iron.
Old Pontiac books say using Torque plate makes .0002

[87vette81big]

2/10,000 Ths difference

Mopar Bob made his own torque plate for his Mipar Wedge 383/440's.
He can make for me a Pontiac V8 Torque plate.
Pattern used from a Fel Pro 1016 Race gasket.
What do think Grumpy ?
Any tips ?

[87vette81big]

Not many shops with torque plates for other engines besides sbc & BBC.

[grumpyvette]

2/10,000 Ths difference

Mopar Bob made his own torque plate for his Mipar Wedge 383/440's.
He can make for me a Pontiac V8 Torque plate.
Pattern used from a Fel Pro 1016 Race gasket.
What do think Grumpy ?
Any tips ?

tips/ not really I'm sure your well informed,
but like you stated I find its a bit odd that I find most machine shops are instantly able to quote the cost to "TORQUE PLATE HONE" several of the less popular engines like the pontiac, olds, AMC caddy, and early hemis etc. yet they don,t own the required TORQUE PLATE, and in some cases I don,t think they care or want to discuss that minor technicality
(years ago the thinking was that because the second rings did not endure the same high temperatures as the top ring the second lower ring could have less gap as it would expand less from heat, modern thinking resulting from testing shows the second ring should have a slightly wider end gap to prevent the stop ring from loosing its seal pressure and developing RING FLUTTER at higher rpms, the problem is that "higher rpms" differ with every combo built)

bores must be honed with a deck torque plate to simulate the stress of a installed cylinder head stress , the torqued bolts exert on the bore walls, the torque plate induces and duplicates that stress so that the bore walls will be pulled into the same relationship when you hone the walls concentric, rings won,t seal correctly in a non concentric bore

gaps must be correct for the application
RINGS MUST BE MEASURED WHILE SQUARE IN THE BORE< A RING SQUARE TOOL HELPS, I USUALLY PLACE THEM ABOUT 1" DOWN THE BORE THEN MEASURE END GAP, see later in the thread for how to make a good but dirt cheap ring square tool

ring ends must be, correctly gaped, cut parallel and de-burred before installation

[87vette81big]

I found what I need Grumpy Google searching.
I am well informed. Never misunderstand me.
I bought a BHJ Pontiac V8 torque plate for myself.
Only 1 engine machinist I trust.
Close friend.
Only chevy guts ge special treatment.

Be sure to delete my accpynt on Digital Corvette Forum.
All mt past 2 years pists too.

[grumpyvette]

YOU CAN GO AND DELETE your POSTS BUT I CAN,T,do more than a couple before Id get blocked, SIMPLY BECAUSE IF I DO ALL MY CHANGES ARE temporary AND HELD IN A MEMORY BACK UP JUST BECAUSE IM A MODERATOR AND THEY HAVE A BACK-UP TO PREVENT MASS DELETIONS EXCEPT BY ADMINS

[87vette81big]

The only Positive thing I can note today is You found me & broght me here Grumpt.
DC is worthless. No Backbone.
Just the old timers & me.

[87vette81big]

The only Positive thing I can note today is You found me & broght me here Grumpt.
DC is worthless. No Backbone.
Just the old timers & me.

[87vette81big]

I am tonight ashamed to be a Corvette Owner Grumpy.
When I think of that group, Fucked up leadership, jackoff jackasses I can't help but wonder why I tried to help.
Like wasted time & years of my life.
I don't think many appreciated.
They won't even get rid of a criminal thief vendor supporter.
$$$ More important than the guys.
Not how I work or was taught by Bill.
No regrets walkng away.
Thier loss.

BR

[87vette81big]

Its Anti Corvette Year Theme Grumpy.
Time to Hook up with my old Gang.
5.0 Mafia.
& others.
Spank every Vette owner on the street & track.
Store bought not enough. Must be made as you know.
I will help them again.
All that HP & Torque has to go somewhere.
The rear diff.
Jackoffs can't get the job done.
Playing with thier nutsacks.

I am the Best.
Still.