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piston wrist pins, one really over-looked part.

PostPosted: December 29th, 2008, 8:15 pm
by grumpyvette

stock wrist pins and the combo of forged piston and longer connecting rods allowing a higher pin or compression height piston,of lower total weight,especially when compared too cast pistons which are rather heavy and often are over looked,as a potentially upgraded component. thinking thru the use of all the components used and what they are made of and the weight , has benefits, those, components made of stronger and lighter aftermarket forged pistons with free floating piston pins (wrist pins)made from tapered tool, or even rather exotic titanium alloy, steel wrist pins can be used to reduce significant reciprocating weight ... 37_104.htm

viewtopic.php?f=50&t=11029&p=48839#p48839 ... m#cxrecs_s ... ad&F_id=36

viewtopic.php?f=53&t=5064&p=14370#p14370 ... index.html
Install Tru-Arcs with the open ends pointing down only and make sure the flat side (with the sharp corners) faces out.

if you have free float piston pins your most likely familiar with these


taper pins are lighter because the internal diameter is thinner towards the outer ends this reduces weight without reducing strength IF THE STEEL USED IS TOP QUALITY HEAT TREATED TOOL STEEL, BE AWARE there CHEAP SUB STANDARD CLONES that are not as well made.. quality aftermarket tool steel ,tapered tool steel piston pins usually cost $15-$30 EACH


in rod for full floating pin, to snap ring (End play 0.0 - 0.005"
the stock style piston pin is usually fairly heavy
the aftermarket ,tapered style can be just as strong, or even stronger due to better materials and heat treating of the component, better hardening, tempering etc. and several grams lighter in weight allowing smaller crank counter weights and lower balancing costs
Most guys order a set of pistons or a rotating assembly and never think for two seconds about the wrist pins that are usually included, but that's a mistake in some cases.
yes the tapered pins cost more but they also tend to weigh less and thus put less stress on the engine at high rpms.
most piston wrist pins look like thick tubes with a mirror chrome finish, but theres also better quality wrist pins available made from far stronger and more expensive steel or titanium with the internal area rather hourglass shaped, where the hole thru the center tappers from a large outer end to a smaller central diam. that saves weight without sacrificing strength
OBVIOUSLY the PIN BUTTONS upside down here to better show the ring clearance groove, it might seen that the pin retention buttons will wear the bore but in most cases the combined length of the two buttons and piston pin were several thousands less than bore diam, and in many cases the lower oil rings retain the buttons

BACK IN THE 70s pin buttons were used as they made free float piston assembly easy and in cases where the pin intersected the oil ring they helped support the oil ring
When a pressed pin is installed,into,and held in place by the small end of the connecting rod being an interference fit in a connecting rods small end, where during use its clamped firmly in place, most shops put the smaller end of the connecting rod on a connecting rod heater device that heats the piston pin end of the connecting rod to specific heat range so it expands slightly.(just enough to allow the pin to slide thru easily) With the piston sitting is a little V-block or rounded cradle, they put the rod into the piston in line with the pin bore location centerline and insert then press in the pin. The pin slides in easily since the hole in the rod has expanded, by the heat, but. Once the rod contacts the pin and piston these act like a heat sink, drawing off heat rapidly so it cools rapidly , the hole in the small end of the connecting rod tightens up as it contracts and the pin will not slide from its location. This takes only a few seconds to contract because the pin, piston and rod body draws the heat out, as soon as the heat source is removed.
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To remove the pins, you don't have the ability of being able to heat just the small end of the rod up with the heater so that it alone expands and allows the pin to slide out. You have to press it out, with a hydraulic press and the pins soaked in light oil then pressed out in a jig that holds the piston assembly.
The piston body being aluminum is easy to deform and its the piston that is resisting the forces of the pin removal hydraulic pressing operation.
pistons and pins should be carefully cleaned with a solvent bath then the pin lubed before dis-assembly to prevent damage from micro crud thats likely to form in a running engine on the piston pin bores.

FULL FLOATING , piston pins are a slide fit in both the small end of the connecting rods and the piston pin bores and are allowed to rotate freely in both the small end of the connecting rod and the piston pin bores, this reduces friction and allows easy hand assembly, but it requires the use of locking snap rings or spiro-locks to hold the pin in its intended location in the pin bore in both the small end of the connecting rods and the piston pin bores. because the small end of the connecting rod has a pin that moves this end frequently has a bronze sleeve inserted and an oil hole drilled to increase lubrication on the piston pins


Guys frequently ask me why I don,t refurbish stock rods or use pressed in piston pins on 90% of my engine builds, its for both economic and strength reasons,
let me say this, Ive build close to 180 engines or more MINIMUM now over 40 plus years (I lost count)and I use the local machine shop to instal pressed in pins or I talk the guys into free float piston designs and I OWN a 12 ton press and several torches, simply because its a P.I.T.A. to fix if you screw it up,and cheap to have done.
now obviously I could buy a rod heater and have the tool, but just using the far stronger aftermarket connecting rods and free float pistons makes far more sense to me, than screwing around with weaker rods and harder to assemble pistons
a good aftermarket connecting rod with 7/16" ARP rod bolts and a cap screw rod design with free float piston pins is easily 150%-200% stronger than refurbished stock connecting rods and after all the time and effort and new rod bolts , polishing, magnifluxing, resizing etc, it just makes zero sense to refurbish inferior rods or deal with press in piston pin

this is were the SPIROLOCS give you a noticeable advantage, they are basically a semi flat spring,with one flat side and one slightly micro-curved side, you pull them out to stretch them then spiral them into place (two slightly curved side BACK TO BACK) flat sides facing out, they act as mini springs taking up any residual space thus keeping the piston pin centered, and resisting any length wise travel.

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Re: piston wrist pins, one really over-looked part.

PostPosted: December 30th, 2008, 4:17 pm
by grumpyvette
my rods are press pin pistons and I was told to heat them in a rod furnace then drop the pins in to install them?

YES thats commonly done that way, and with stock pistons and rods you can do that, but Ive always said if your going to get decent pistons and rods get the full float style, the pins rotate in both the pistons and rod for less friction, the pins smaller and lighter and the pistons tend to be far better quality, and you can assemble and dis-assemble the rods from the pistons for inspection by hand!
while were talking about installing stuff thats a press fit....
heating bearings enough to expand them a good deal,is usually a BAD IDEA!
it can burn off protective finishes
it can distort the clearances
it can ruin the heat treatment
it can warp the surface finish
it can ruin the bond to the backing material,
it can cause soft spots in the surface, etc.

you can usually find these on sale for under $120 ... mber=33497

yes its a total p.i.t.a. to take the differential out to work on it, but at times its the smart choice.

Obviously if your only running the temp up with something like a hair drier or a heat gun to 140f-250f or so as oil always gets that hot, its most likely having zero bad effect, but by 400F PLUS if not controlled correctly , can easily cause problems in some rare cases,
400F is not a problem, pistons normally see that temp range occasionally, but anytime you say HEAT,IT UP! to most guys...
out comes the propane or acetylene torches,and all precise control on temps becomes a joke.
IVE gone the reverse route in most cases and packed cranks, axles, piston pins, etc in dry ice for an hour or so then spray them with a fine mist of oil and in many cases you can slip bearing into place if the clearances are just a bit tight.
a HYDRAULIC PRESS is a great tool, but the truth here is that 99% of the pressed in piston pin applications are best handled with a local machine shop having the correct rod heater and tools required rather than having you do it yourself

Btw I haven’t (VOLUNTARILY) used or advised the use of pressed pin pistons, in connecting rods for years, IVE always preferred bronze bushed rods with free float piston pins and dual spirolocs on each end of the wrist pins or dual internal spring clips

Re: piston wrist pins, one really over-looked part.

PostPosted: August 27th, 2010, 11:55 am
by grumpyvette
IF you've ever needed to use spiro -locks ,READ THRU THESE LINKS ... index.html ... index.html

Spirolock Tool
What company makes a spiral-lock installation tool? Sore fingers and thumbs from installing the locks into pistons is a real drag.
Randy Guynn
Pasadena, TX

We've all got plenty of old wounds from installing Spirolocks in pistons and hose ends on stainless steel braided hose. Piston pin bores can also get torn up by the small screwdrivers often used as improvised Spirolock installation and removal aids. The solution is, of course, getting the right tool for the job. For piston pin locks, Lock-In-Tool sells Spirolock as well as round-wire-lock installation tools; they're available in 4140 hardened steel for repeated use by the professional engine builder or in more affordable lightweight plastic for the home builder. Order by type of retainer (Spirolock or round wire), tool material (steel or plastic), and piston pin diameter. Also available from Lock-In-Tool is The Lockbuster, which makes short work of removing those pesky Spirolocks.
Lock In Tool Spirolock Tool
The Lock-In-Tool is available...

read full caption
Lock In Tool Spirolock Tool
The Lock-In-Tool is available for most popular pin diameters in steel and plastic. These examples are for 0.927-inch-od small-block Chevy pins. The steel version (left) fits spiral-type locks; on the right is a wire-lock installer in plastic. The clip inserts into the opposite pin groove to prevent the pin from sliding out of the piston during initial installation.

Spirolock In Action
Using the installer, Spirolock...


read full caption
Spirolock In Action
Using the installer, Spirolock installation now takes seconds instead of minutes. Simply spin the lock onto the tool until the end of the lock aligns with the tool's registration mark. Tilt the tool slightly to the left and insert it into the pin bore to place the lock into the groove. Square the tool and turn counterclockwise until the lock spins completely into the groove.

Waxhaw,NC 704/843-5477

Piston Pin Spiro Lock Installation Procedures

When the locks are properly seated, only half of the lock will be visible above the groove. Most pistons that require spiral locks will need four locks per piston, two at each end of the pin (check with your pistion supplier).

When installing Spiro locks, grip each end of the lock and pull apart (approx. 3/8˝-7/16˝). The lock will resemble a small coil (Figure 1). The lock can then be spiraled into place almost as if you were screwing them into a groove (Figure 2).

WARNING:It is important that the correct numbers of locks are installed in each piston or severe engine damage may occur. Do not over stretch spiro locks and do not reuse spiro locks.

–Tech Tip courtesy of JE Pistons

Re: piston wrist pins, one really over-looked part.

PostPosted: January 16th, 2011, 4:50 pm
by grumpyvette

Re: piston wrist pins, one really over-looked part.

PostPosted: April 3rd, 2011, 11:43 am
by grumpyvette
Connecting Rod Reconditioning: More to it than you might think

The processes used to recondition connecting rods may vary a little from one rebuilder to the next, but the end goal is always the same - straight rods with round bores

By Brendan Baker

Brendan Baker

The connecting rod plays a vital role in the engine. But a connecting rod is under tremendous stress, with the weight of the piston sitting on top, changing direction thousands of times per minute. This continuous stopping and changing of direction combined with the weight of the piston and speed of the engine hammer on the bearings and torture the rod bolts which hold everything together.

Proper geometrical alignment and bearing surfaces that are smooth and perfectly round is the best way to ensure long engine life and happy customers. Any unwanted lobing, chatter or misalignment, particularly in engines that operate at high rpms, will affect the engine's efficiency.

One of the most important aspects of rebuilding an engine is to recondition the connecting rods. There are many different types of connecting rods from cast steel to powdered metal "cracked" rods to all the various types of performance rods. The processes used to recondition this engine component may vary a little from one rebuilder to the next, but the end goal is always the same - straight rods with round bores. Sounds simple, but like anything worth doing, there's always more to it than you think.

Typically, reconditioning rods involves cleaning them thoroughly, then checking them with magnetic particle inspection for any cracks. Then the rods are checked for straightness because any bend or twist in the rod may result in oil clearance problems and likely lead to a failure.

A visual inspection of the rods will also include looking for any signs of overheating, which may be indicated by a "bluish" appearance. If the rod has been overheated, its structural integrity may have been compromised, according to the rebuilders we interviewed for this article.

"If a guy has overrevved his engine, we go through and magnaflux all the parts," says Kenny Burns, Harry's Machine Works, Dodge City, KS. "Connecting rod material is typically pretty good, but sometimes the machine quality leaves something to be desired. Therefore, we check everything, even brand new rods."

On the performance side, some rebuilders will check the hardness before declaring them fit for the junk pile. "You can test the heat treatment with a Rockwell tester," says Roger Friedman, Dyer's Top Rods. "We know what our rods should be. They're usually in the 42-43 range on the Rockwell C scale. If a rod got hot enough to change that, it's junk to us."

Friedman cautions that color isn't always a true indicator, however. "We'll sometimes see some rods that were affected when an oil pump belt came off, for example. If you catch them soon enough, they will still turn color, but if the rods test okay, we will shot peen them, re-cut and resize them and reuse them."

After the rod has been cleaned and inspected thoroughly, it should be put back together with the rod bolts torqued. With a stretch gauge, check each rod bolt for proper stretch. If the stretch is out of spec, then replace the bolt. While some engine builders say that it is safer and less expensive to just replace the rod bolts instead of measuring the stretch, others say that practice really depends on the application, because some high performance rod bolts can be quite expensive.

After the caps are torqued on with acceptable rod bolts, measure the big end bores. This will help you to determine how much to take off the caps and to what size you'll need to hone them. In general, you want to take off as little material as possible to make the bore round again. After you hone the big end, measure the rod to see what size bushing you need to put in the pin end.

"The ultimate goal when reconditioning rods, is to come up with a set of rods that are straight and of the correct length," says Jay "Dr. Diesel" Foley, of Foley Engines, Worcester, MA. "In common four- and six-cylinder gasoline and diesel engines, the rods must be machined back to original specs with no more than .0025" of bend and no more than .00425" of twist. A rod with too much bend will limit oil clearance from one side to the other and possibly lock up the engine at the pin end or at the thrust on the crankshaft. In addition, they must have round and concentric bores, and the fasteners must also be able to withstand the stresses of a modern engine."

Once the connecting rods are bored and honed, then you can put the proper size bushing in the small end, which itself is a very important step. "We are very concerned about the piston-pin bushing relationship," says Foley. "We always press out the old piston-pin bushing and install new ones. But that is only half the battle. To ensure that the bushing won't rotate, we expand it to conform to the small end bore. To expand this bushing we press a hardened steel ball through the ID of the new bushing. This will lock in the new bushing and prevent it from spinning in the bore. If you heat the rod to install the new bushing, you should allow it to cool before you expand the bushing with this broaching technique. Then grind the cap to the correct center-to-center dimension and hone the big end and install new rod bolts."

According to Harry's Machine Works' Burns, keeping the rod straight is very important. However, one of the difficulties his shop faces is finding aftermarket wrist pins that are the correct size. "Some aftermarket suppliers are making wrist pins that are supposed to be the same size as OE but they are not," he explains. "We have had a hard time trying to get the right sizes. Sometimes the pins are .001? to .003? off the OE specs. Within that application we have seen differences of up to .003? and we're trying to keep the tolerance within .0002" to .0003"."

Burns says that his shop uses a similar process to Foley's for reconditioning connecting rods. Both Foley Engines and Harry's Machine primarily rebuild diesel engines. Rebuilding diesel rods isn't much different than gas engine rods, except they're much bigger and the center-to-center distance is has to be exact. Since diesel engines operate on a compression cycle, rod lengths have to be correct. "We can shorten them or lengthen them," Burns says about diesel rods, "it just depends on how much has been taken off the block. So the center-to-center distances are critical."

Fractured Rods
Fractured rods are a fairly new phenomena. Ford was one of the first on the automotive side to use a fractured rod in the 4.0L engine, which was one of its first new generation engines in 1990. The fracture method has proven to be less expensive for manufacturers and it produces better quality because it is forged in one piece and then 'cracked' at the rod cap.

"Before fractured rods were invented, conventional rods were two components," says Dave Hagen of the Engine Rebuilders Association (AERA). "You would have one piece, which was the cap and another that was the beam. The two pieces were close enough to bolt together; then you would have to do several machining operations to get the center-to-center distances correct. The fractured rod, on the other hand, is a powdered metal rod that allows the manufacturer to pop it out like an egg with very little machining to make the size exactly right. It comes out essentially the final size and then is broken at a scored line that is part of the design. Once it's broken or 'cracked,' it's done. It can be manufactured for far less cost than a traditional rod and it's a more durable component."

According to Hagen, the inside diameter of a fractured rod bore is scored and then some pressure is applied until it snaps. The resulting split is like a piece of china that has been broken. It has a very distinctive surface that custom fits together. The fracture has more surface area because you have peaks and valleys, and the alignment is more accurate since the cap only fits together one way.

For rebuilders, there's not much you can do with fractured rods. You can't cut the caps because of the unique break on each one. And for the most part, you cannot hone the bore because there are very few oversize OD bearings available for them. Hagen says that some suppliers carry oversize OD bearings for the big end of the more popular models, like the modular 4.0L and 4.6L Fords, but it's uncertain if there are any bushings available for the pin end. So there's a little bit of rebuildability with fractured rods but not much.

Now, some heavy-duty manufacturers are going to fractured rods. "There are some heavy-duty manufacturers making them, like John Deere is coming out with some now, but with fractured rods we can't do much with them," acknowledges Harry's Machine Works' Burns. "We measure them to check the size, and that's about all we can do until there are oversize OD bearings available."

New Methods
For years, connecting rods have been honed on specialized rod honing machines, which are available from many leading manufacturers. These machines have been the standard, produce excellent results and are still widely used throughout the industry. However, Sunnen and Rottler have both recently come out with new systems that take a totally different approach to rod reconditioning.

Sunnen's system is called the KGM-1000 Krossgrinding System®. The KGM system utilizes an easy-to-use computer control, diamond tooling and a feed system that gives the operator high accuracy and speed in the production of precision reconditioned connecting rods. The company says the system is extremely accurate for honing connecting rods, and is capable of holding very tight tolerances, achieving accuracies of .00001" in straightness and .00015" in roundness.

Rottler has also designed a completely new system that works with the F-65 and F-67A multi-purpose machines. According to Rottler's Anthony Usher, the company wanted a system that could bore both the big end and the small end in one setup.

"When we decided to get into the rod reconditioning business," Usher says, "one of the big problems we saw was that rods bend and twist. When you have two setups you can sometimes create other problems. We decided to design a system where a rebuilder could lay the connecting rod horizontally and set it up so both the big end and the small end could be open. With both ends open you can machine both ends in one machine and in one set up and achieve perfect parallelism between the centerlines of both ends."

Rex Crumpton Jr., of Memorial Machine in Oklahoma City, OK, says his shop has both a Berco rod honing machine and a new Rottler system. According to Crumpton, both systems work excellent and he can achieve good results either way. Memorial uses the Berco machine for doing smaller stuff and the Rottler for reconditioning larger rods.

"Honing is excellent, there's nothing wrong with doing rods that way," says Crumpton. "But boring can be a bit more precise. You don't have to worry as much about stones loading up, which could produce taper. As long as you have a good operator who is paying attention, both methods work fine."

Re: piston wrist pins, one really over-looked part.

PostPosted: August 18th, 2011, 6:27 pm
by grumpyvette
Written by David Reher

I come from a family of teachers, so perhaps I’m genetically programmed to stand in front of a classroom. Maybe that’s the motivation behind the engine building classes that we conduct regularly at Reher-Morrison Racing Engines. What I’ve discovered, however, is that a teacher learns as much from the students as the students learn from the teacher.

When a racer attending one of our seminars asks why we prepare a part a certain way, I have to think about the experiences that led us to adopt a particular technique or choose a specific engine component. A case in point is the lowly wrist pin – one of the most overlooked yet most important components in any motor.

The wrist pin is a crucial link in the chain that connects the power to the pavement. It has to withstand the full force of the cylinder pressure while accelerating several thousand pounds of race car. Yet racers who will gleefully study cylinder head airflow graphs and camshaft profiles for hours seldom give any thought to the wrist pins in their engines. Let’s face it: Wrist pins simply aren’t sexy.

I’ve built racing engines for more than 30 years, and have always subscribed to the belief that lighter is better. But recently I’ve had to reevaluate my thinking in regard to wrist pins. I’ve come to the conclusion that as power levels have escalated, many racers are using wrist pins that are just too light. I’ve also realized that some of the parts that extract more horsepower from an engine also increase the stresses on the wrist pins. Racing isn’t exempt from the rule of unintended consequences: Every solution breeds new problems.

When selecting parts for a racing engine, the general rule is “light is good.” For example, a lightweight crankshaft assembly require less power to accelerate than a heavy crankshaft assembly, and therefore more of the engine’s output can be used to accelerate the race car. But if the parts are so light that they deflect and deform under high loads, then the result is the exact opposite – more friction is created and more power is siphoned off in the form of heat that destroys the pins, pistons, and connecting rods.

In reality, more power equals more cylinder pressure, so we have to select parts that are appropriate to the engine’s power levels. Once you go beyond a set of off-the-shelf pistons, the choices of wrist pin material, diameter and wall thickness become critical.

When a customer orders a set of wrist pins, the first question I ask is, “How powerful is the engine you’re building?” A set of tool steel wrist pins with a .090-inch wall thickness might be fine for a small-block Super Stock engine, but a 1,000-horsepower big-block typically needs pins with .150-inch wall thickness – and the pins must be correspondingly thicker for a nitrous-injected engine. The wrist pins used in blown alcohol and nitro-burning engines illustrate just how strong the pins must be to survive under extreme conditions.

A catastrophic pin failure is an expensive way to learn that the pins are too light. Fortunately there are some early warning signs that indicate the pins are overstressed. Black streaks in the pin bosses or the small ends of the connecting rods are danger signs. In more advanced cases there may be aluminum welded to the pins from the piston pin bosses and rods (in the case of aluminum rods). With steel rods, look for signs of distress in the bronze bushings in the small ends of the rods. These problems are usually the result of wrist pin deflection, insufficient clearance or inadequate lubrication.

Wrist pin problems were rampant in Pro Stock several years ago, and the cure was to apply some very expensive coatings. Spending $800 for coated pins is not a cost-effective solution for most sportsman racers, however; the object is to make as many runs as possible at a reasonable price. Assuming that the wrist pins have adequate strength, it’s possible to head off many problems simply by ensuring that the pins have adequate clearance and lubrication.

The crankcase in an engine with a conventional wet-sump oil pan is awash in oil. If there is a condition that’s heating up the wrist pins or stressing the piston and rod bores, the sheer volume of oil in the crankcase will carry off the excess heat. But a well-designed oil pan with a kick-out, crankshaft scraper and a vacuum pump (or a good dry-sump system) will dramatically reduce the amount of oil in the crankcase. While an efficient oil system reduces windage and increases horsepower, it can also put the wrist pins in jeopardy – another instance of unintended consequences. In fact, the wrist pins in the even-numbered cylinders are often the first to show signs of distress caused by insufficient lubrication because they are on the side of the engine that has much of its lubrication stripped away by the crankshaft scraper and oil pan kickout.

In this situation, my recommendation is to increase the wrist pin clearance. Most engine manuals recommend wrist pin clearances between .0008 and .0010-inch for conventional engines; my advice is to run .0020 to .0022-inch wrist pin clearance in a serious drag racing engine. My perspective on engine clearances is straightforward: When in doubt, a little loose will seldom result in catastrophic failure, but a little too tight will almost always cause problems.

Remember that drag racing engines are usually stone cold when they go down the race track. We start the engine and get to the staging lights as quickly as possible because a cold engine makes more power than a hot one. Consequently drag racers don’t have the luxury of an extended warm up period to bring all of the parts up to operating temperature. In these circumstances, a little extra clearance is a good thing.

I’m an advocate of double Spirolox pin retainers. Yes, they are a pain to install and remove, but that’s exactly what’s needed in a pin retainer – a lock that won’t come out on its own.

Wrist pins aren’t glamorous, but they are absolutely essential to the health and well being of a racing engine. Don’t scrimp on pins; a few extra grams of wrist pin weight can increase your engine’s life expectancy. ... 7ibJ7FwU4M ... wordSearch