piston related info

[grumpyvette]

THERES A GREAT DEAL OF GOOD INFO IN THE LINKS ,YOULL BE CHEATING YOURSELF BADLY IF YOU DON,T READ THE SUB LINKED INFO



If your looking for new pistons do some research, youll need to know the bore size, stroke, rod length, piston pin type,piston ring design , and at least a general idea on combustion chamber and valve size, valve diameter, and intended valve lift and cam timing to get clearances correct.and several other related facts before you can select the correct piston
lets look at your options, obviously both your intended use and/or rpm range will effect the logical options as will your budget.
your first option is between cast, hypereutectic and forged alloy pistons, cast are generally cheap and function well under low heat and load like normal driving, hypereutectic have a much stiffer alloy that
has silicone added and these are slightly stronger, forged are significantly stronger , less likely to break,but more expensive
your second common choice is selecting between 5.7" and 6" connecting rods.
your third choice is between pressed and full float wrist pins.
your fourth choice will depend on compression ration desired.

examples, of cast and hyper pistons for a common 350-383 sbc, usually cost about $170-$250 per set of 8
forged will commonly run in the $370-$500 range per set but will be a better option if nitrous is used or you intend to run over 4000 feet per minute in piston speed frequently
I HAVE ALWAYS PREFERRED FULL FLOATING PISTON PINS
(that way you can self assemble the piston on each connecting rod)
(which comes in handy when you need to change piston deck height/quench, and side clearance etc.)
AND CUT TO FIT RINGS
(which allow a true custom fit)
and if possible forged pistons
(which are more durable and less subject to as rapidly occurring damage from detonation)
now I have zero problem using hyper-eutectic pistons in the proper applications because they work as well or at least as well as required with little or no down side if you remember the previous stated limitations


related info
http://www.kb-silvolite.com/calc.php?action=piston

http://www.jepistons.com/TechCorner/HowToIdentify.aspx

viewtopic.php?f=53&t=110&p=31943&hilit=2618+4032#p31943

viewtopic.php?f=69&t=7804&p=30277&hilit=2618+4032#p30277

viewtopic.php?f=53&t=4516&p=16279&hilit=2618+4032#p16279






http://www.babcox.com/editorial/ar/ar80125.htm

http://en.wikipedia.org/wiki/Hypereutectic_piston

viewtopic.php?f=53&t=5454

viewtopic.php?f=53&t=5064&p=14370#p14370

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

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

viewtopic.php?f=53&t=509&p=632#p632

http://www.circletrack.com/techarticles ... index.html

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

http://www.aa1car.com/library/2003/eb40354.htm

http://kb-silvolite.com/article.php?action=read&A_id=5

http://kb-silvolite.com/article.php?action=read&A_id=1

http://en.wikipedia.org/wiki/Hypereutectic_piston

http://forums.nasioc.com/forums/showthread.php?t=907570

http://www.circletrack.com/techarticles ... index.html

viewtopic.php?f=53&t=509&p=868&hilit=+total+seal+gapless#p868

http://www.techlinecoatings.com/article ... rticle.htm

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



read these links

http://arp-bolts.com/pages/technical_failures.shtml

http://www.hotrod.com/techarticles/stee ... index.html


here is where you, or your machine shop can screw things up on ring to bore seal, you need to have the cylinders bored and honed to the correct size specified by the manufacturer of the pistons,after MEASURING THE PISTONS to verify their size per the piston manufacturers instructions, then gap the rings per the ring manufacturers instructions, 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, keep in mind the piston side clearance must match what the piston manufacturer states.

[grumpyvette]

heres a quote from keith black pistons, concerning piston alloys
http://kb-silvolite.com/article.php?action=read&A_id=38

" PISTON ALLOYS AND HIGH PERFORMANCE

Which alloy is strongest? Answer, it doesn't matter. All piston alloys used by the industry today are strong enough, including cast iron. The real story is in more technical terms like fatigue strength, thermal conductivity, wear resistance, expansion rate, coefficient of friction and specific gravity.

Thermal conductivity is probably the least understood of all terms as it applies to a piston running in an engine. The effective conductivity of a piston (not the alloy) can be altered with coatings, surface area, section design, polish, and top land design. Ideally, the combustion surface of a piston would run at a little over 500°f and not exceed 600°f. The 600°f not-exceed temperature is the most important when it comes to engine life because a 600°f piston top can ignite the fuel mix independent of the spark plug.

Our performance is that we will make higher Hp and better low RPM torque with the best economy and smog numbers. It also suggests that we will have to maximize design efforts to cool the piston to keep the piston top below 600°f. On the opposite end of the spectrum regarding thermal conductivity is our forging alloy 2618. It is the most conductive alloy used by anyone making performance pistons. When the top gets hot the whole piston gets hot and expands accordingly. Noisy when cold and just fine when warmed up. The relatively cold piston top does hurt low RPM power and economy some, but design features can offset some of the shortcomings. Some forgings have been made with a slot at the oil drain back area for the purpose of restricting heat flow to the skirt. The design works and allows forgings to run almost as tight as hypereutectic pistons. Unfortunately, the heat slot weakens the piston below what is required for modern high Hp engines.

The coefficient of friction of all materials is pretty much the same when lubricated as the oil really determines how much slip you have. The unlubricated condition is the important number, especially since it is closely tied to wear and gauling. An engine seeing detonation tends to burn the oil off the cylinder walls. The surface finish on all KB Pistons is designed to put the oil back, but severe detonation can produce a situation with a dry cylinder and a tight piston. The hypereutectic alloys, those with at least 16% silicon (4% free particulate), have a structure somewhat similar to fiberglass. This hypereutectic alloy will slide on the free silicon when oil is not present. This phenomenon is what is responsible for the almost never-gaul never-wear reputation of KB Hypereutectic Pistons.

Specific gravity of piston alloys does affect the weight. Keith Black did make some magnesium pistons that worked. For the most part, though, most lightweight materials tried as piston material fall from thermal conductivity, wear, or fabrication problems. Currently the big savings in weight comes from design changes and the use of real long connecting rods.

Expansion rate varies from aluminum alloy to aluminum alloy with about a 15% total spread. Our forged pistons expand about 13% more than our hypereutectic. Big deal! 15% of 2/1000's of an inch is only .0003". Twice, nothing is still nothing. Why can't we run .002" clearance on performance forgings? The expansion of a piston is controlled by two factors, coefficient of thermal expansion and temperature. The expansion rate is the small player, but the temperature is drastically affected by the thermal conductivity of the piston. All successful forging alloys send combustion chamber heat to the piston skirt quickly, and hot skirts require the extra skirt clearance.

Strength and ductility are often confused terms. Most all pistons are more than strong enough at room temperature, with a slight edge going to the forging alloys. At high temperature the hypereutectic alloy has the edge strength-wise. The problem is if your pistons are 800°f and strong the engine is hypereutectic alloy is a slow conductor of heat. The benefit in in detonation mode and will continue to escalate temperature to destruction. (Direct injection engines may allow higher piston top tempertures.) Ductility is the main area where forging alloys really win. Short of breaking a wrist pin, forgings usually stay attached to the connecting rod even with nuts, bolts, and valve heads sharing the same combustion chamber space. A dropped valve on a forging is more likely to stick in the piston and limit damage to the cyliner head, rod, and piston.

In summary, we make forged 2618 and 18% hypereutectic pistons to hopefully offer the best piston choice to the end user. The hyper pistons have been designed to run forever and are a little more high tech. The forgings are safe. They are excellent when used in development type engines and some very high heat engines. Top fuel and 5 Hp/cubic inch plus engines see a lot of heat, and it is a little easier to cool a forged piston top. Hypereutectic pistons are a little less likely to form cracks than forgings because the alloy structure is somewhat like fiberglass. Cracks occur from flexing. The KB Hyper Pistons are designed not to flex. If the engine builder leaves a rod bolt in the intake, this soon becomes a component flex test. There are no winners ... and piston, cylinder, and cylinder head are usually proven not very flexible.

John Erb
Chief Engineer
KB Performance Pistons
"

[grumpyvette]

info thats well worth reading thru
http://www.hotrod.com/techarticles/hrdp ... index.html

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

http://www.rosspistons.thinkhost.com/re ... LATION.pdf

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

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

http://www.flatlanderracing.com/trwchevy350.html


Piston Alloy Comparison
4032........................... ................................2618
High silicon ......................................... ...........No silicon
Low expansion ................................... .........High expansion
Tighter piston-to-wall clearance . ...........More Piston-to-wall clearance needed
Quiet Operation .................................Noise when cold
Less ductile ........................................... More ductile
More stable & consistent.................... ...... Higher resistance to detonation
Longer life cycle.............................................. Shorter life cycles
Harder .................................................... ........Softer


Now IVE used HYPEREUTECTIC, and both common forged alloys
The experiences I’ve had seem to be that hypereutectic pistons work great up to the point you get into detonation, and then they fail rapidly and catastrophically, if subjected to the head and pressure, coming apart in chunks.
The forged pistons in either alloy will sustain a great deal more abuse without showing it for much longer but ANY piston subjected to detonation will eventually be destroyed.
Hypers are almost BRITTLE, in comparison, and while bouncing a valve of any piston is a very bad idea, the forged pistons are usually scared, and nicked if the impacts minor, hypers can break apart. Leading to much larger problems than a simple bent valve.
AND you will eventually float valves or run into detonation with any engine your racing and pushing for every last bit of hp. or alloying the engine to run a bit lean at some point, especially with nitrous, or a supercharger.
So if your building a serious combo Id suggest thinking seriously about forged pistons but as the manufacturer for the correct clearances and part numbers and carefully follow the installation instructions.




when ever you order parts like pistons that must be fitted precisely to a block,ok the first factor you need to know is the TRUE bore diam. of the block, and if its consistent between all cylinders, youll also need to know the deck height on the block, the connecting rod type, IE, is it set up for pressed or floating pin pistons and if the block ,decks parallel and square to the crank center line, you'll need to order pistons that fit the bore or in most cases you order pistons a bit larger than the current bore size and have your engine builder bore, hone and fit the pistons to your block with the correct side clearance, and order a matching ring set.
the cylinder heads combustion chamber shape , you chose to work with and location in the cylinder heads of that combustion chamber will determine BOTH the dome or dish size, the pistons require to function correctly and the valve clearance you need, along with the cam you select and the way you degree it in to the engine.
remember different piston materials expand at different rates and require different side clearance and ring gaps.(don,t forget that different rings will require a different surface Finnish on the bore surface)

as a general rule HYPER-EUTECTIC pistons will require a tighter bore clearance and more ring gap clearance than forged pistons as they tend to run hotter and expand less in the bore, but you MUST use the manufacturers suggested clearance requirements.
not all piston domes are located to clear all spark plugs, valve sizes or combustion chamber shapes, so ask both the piston and head manufacturers for info they might have on potential problems, most engine builder will know how to correct MINOR mis-matches,
but ordering the correct piston machined for the intended application, and carefully measuring components before and during assembly and NEVER taking ANYTHING FOR GRANTED goes a long way toward preventing problems.
factors like the piston pin length and diam. and the piston pin bore thru the piston, the method of locking the piston to the rod and the heat and rpm band your likely to run those pistons under will require some careful thought if you expect the engine to live a long life, surface finish, heat barrier coatings will also effect the choices.
AS LOTS of QUESTIONS before ordering and carefully check clearances during the assembly process.
Youll also want to keep in mind that swapping too new pistons will generally require re-balancing the rotating assembly


a ball hone with 320 grit used sparingly produces a very good surface finish for moly rings to seal with but a ball hone follows the cylinder wall surface even if its a bit egg shaped or hourglass or cone shaped so its NOT going to be ideal in a well worn cylinder because the rings will not be able to fully contact a non-cylindrical cylinder wall.






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
http://www.circletrack.com/enginetech/c ... for_speed/

[grumpyvette]

piston speeds over 4000fpm, tend to be a long term durability issue. over 4500fpm generally ARE getting into excessive stress levels

viewtopic.php?f=53&t=343

http://www.csgnetwork.com/pistonspeedcalc.html

http://www.theoldone.com/articles/engin ... nfacts.htm

http://www.wallaceracing.com/piston-speed-velocity.php

http://2.3liter.com/Calc2.htm#BasAltCal


the piston moves twice its stroke distance per revolution, 4000feet per minute = 48,000 inches, 4500fpm = 54000 inches

example a 350 sbc with its 3.5" stroke =7" per revolution, so 4000fpm =6850 rpm as a fairly reasonable limit with stock components, swap to all balanced and forged components and ARP fasteners and you can push the limits briefly to 4500fpm or 7700rpm but that is very unlikely to allow the engine to live long and remember the valve train probably won,t hold up near that rpm level and your unlikely to make effective power because just filling the cylinders becomes extremely difficult because you need to open the valve, fill the cylinder , burn the mix, exhaust and refill the cylinder 64 times a second at that rpm


RING END GAP CLEARANCE needs to be carefully checked

The piston ring's end gap can have a significant effect on an engine's horsepower output. Rings are available both in standard gap sets, and in special "file fit" sets. The file fit sets allows the engine builder to tailor the ring end gaps to each individual cylinder. Ring gaps should be set differently dependent upon the vehicles use, within the range of .003" (for the 2nd. ring) to .004" (for the top ring) per inch of cylinder diameter. The more severe the use, the greater the required end gap (assuming the use of similar fuels and induction systems). Engines having low operating temperatures, such as those in marine applications is too small. The chart below is a general guideline for cylinders with a 4.00" bore, adjust the figures to match your engine's cylinder diameter:

Top Rings (ductile iron, 4" bore)

Supercharged

Nitromethane .022 - .024"

Alcohol .018 - .020"

Gasoline .022 - .024"

Normally Aspirated - Gasoline

Street, Moderate Performance .016 - .018"

Drag Racing, Oval Track .018 - .020"

Nitrous Oxide - Street .024 - .026"

Nitrous Oxide - Drag .032 - .034"

2nd Rings (plain iron, 4" bore)

Supercharged

Nitromethane .014 - .016"

Alcohol .012 - .014"

Gasoline .012 - .014"

Normally Aspirated - Gasoline

Street, Moderate Performance .010 - .012"

Oval Track .012 - .014"

Pro Stock, Comp. .012 - .014"

Nitrous Oxide - Street .018 - .020"

Nitrous Oxide - Drag .024 - .026"

INSTALLATION NOTES -

CYLINDER WALL FINISH

When installing new rings, the single greatest concern is the cylinder wall condition and finish. If the cylinders are not properly prepared, the rings will not be able to perform as designed. The use of a torque plate, head gasket, and corresponding bolts are necessary to simulate the stress that the cylinder head will put on the block. Main bearing caps should also be torqued in place. The correct procedure has three steps. First the cylinder is bored to approximately .003" less than the desired final size. Next it is rough honed within .0005" of the final diameter. Then a finer finish hone is used to produced the desired "plateau" wall texture. Use a 280 - 400 grit stone to finish cylinder walls for Plasma Moly rings.

Note - the "grit" number we are referring to is a measurement of roughness, it is not the manufacturers stone part number (a Sunnen CK-10 automatic hone stone set #JHU-820 is 400 grit). The cylinder bores should be thoroughly scrubbed with soap and hot water and then oiled before piston and ring installation.

Piston ring grooves are also sealing surfaces, and must be clean, smooth and free of defects. Ring groove side clearance, measured between the ring and the top of the groove, should be between, .001" and .004".

Id call the piston manufacturer and get their tech guys feed back, you'll generally want about a .005 piston to bore clearance with forged pistons but every piston design and manufacturer will have the required specs on file for every piston they make ,that should be carefully followed
don,t forget to ask about ring end gap,ring thickness,ring back clearance and ring groove size, quench distance, compression height, valve notch clearances and cylinder bore hone grits to be used,what piston pin and retainer should be used and what the pistons should weight, always ask "what else should I know?" and "what would be YOUR suggestions here?"


ID suggest trying for a MIMIMUM of .038-.044 on a 496 BBC for quench as the long stroke bbc, or any BBC run over about 6000rpm with a 4" or longer stroke) tends to allow the quench clearance distance to tighten up a bit at high rpms, as parts stretch under stress/inertial loads

[grumpyvette]

http://kb-silvolite.com/article.php?action=read&A_id=1

"
Aluminum Alloys for Pistons

United Engine currently uses gravity feed permanent molds to produce aluminum pistons. Aluminum, alloyed with copper,magnesium, nickel and silicon are common piston alloys in use today.

Silicon is the major alloying element added to the aluminum. It offers a number of benefits in the area of piston production and piston operation.
Machinability Corrosion Resistance
Weight Reduction
Improvement in Hardness and Strength
Improvement in Expansion Characteristics
Improvement in Wear and Scuff Resistance

Aluminum silicon alloys used in pistons fall into three major categories: eutectic, hypoeutectic and hypereutectic. Probably the easiest way to describe these categories is to use the analogy of sugar added to a glass of iced tea. When sugar is added and stirred into the iced tea it dissolves and becomes inseparable from the iced tea. If sugar is continuously added, the tea actually becomes saturated with sugar and no matter how much you stir, the excess sugar will not mix in and simply falls to the bottom of the glass in crystal form.

Silicon additions to aluminum are very similar to the sugar addition to the iced tea. Silicon can be added and dissolved into aluminum so it, too, becomes inseparable from the aluminum. If these additions continue, the aluminum will eventually become saturated with silicon. Silicon added above this saturation point will precipitate out in the form of hard, primary silicon particles similar to the excess sugar in the iced tea.

This point of saturation in aluminum is known as the eutectic and occurs when the silicon level reaches 12%. Aluminum with silicon levels below 12% are known as hypoeutectic (the silicon is dissolved into the aluminum matrix). Aluminum with silicon levels above 12% are known as hypereutectic (aluminum with 16% silicon has 12% dissolved silicon and 4% shows up as primary silicon crystals).

Pistons produced from these alloy categories each have their own characteristics. Hypoeutectic pistons usually have about 9% silicon. This alloy has been the industry standard for many years but is being phased out in favor of eutectic and hypereutectic versions. Most eutectic pistons range from 11% to 12% silicon.

Eutectic alloys exhibit good strength and are economical to produce. Hypereutectic pistons have a silicon content above 12%. r>


It is the primary silicon that gives the hypereutectic its thermal and wear characteristics. The primary silicon acts as small insulators keeping the heat in the combustion chamber and prevents heat transfer, thus allowing the rest of the piston to run cooler. Hypereutectic aluminum has 15% less thermal expansion than conventional piston alloys."



http://kb-silvolite.com/article.php?action=read&A_id=5

"
Hypereutectic -vs- Forged Pistons

Hypereutectic pistons are used in some original equipment engines. They are favored because of reduced scuffing, improved power, fuel economy and emissions.

Hypereutectic 390 refers to a unique aluminum piston alloy that contains dissolved and free silicon. The material can be T6 heat treated to high strength and stiffness. Non-heat treated 390 hypereutectic alloy aluminum has slightly less strength than conventionally cast F-132 aluminum.

With this in mind, we caution the reader about the use of non-T6 heat treated O.E. design hypereutectic pistons for high performance. Silvolite and others do make replacement-type hypereutectic pistons that are worthwhile for stock replacement applications. Original equipment design is almost never suitable for performance applications.

The KB line of hypereutectic pistons were designed around the 390 alloy. The result is a high performance part intended to give the performance engine builder access to the latest in piston technology.

Forgings have long been the mainstay of the performance business and did well in the big cubic inch engines of the 60’s. Now, with focus on peak cylinder pressure timing, ring sealing dynamics, cylinder air tumble and swirl, combustion chamber science, and extended RPM ranges, we need to consider some new piston options.

The KB T6 hypereutectics are considerably different than the forgings. The KB pistons have shown improvement in power, fuel economy, cylinder sealing, service life, and cost effectiveness. The reduced thermal expansion rate allows the piston to be run with reduced clearance. A tight piston is less likely to rock, make noise, and burn oil. A rocking piston wears rings and increases blow-bye. The close fit of the KB piston allows the piston rings to truly seal, minimizing blow-by.

The design flexibility enjoyed by the KB series of pistons has an advantage over present day forging practices. The die for a forged piston must be designed so it can be easily removed. This limitation makes it difficult to make a light weight piston without sacrificing strength.

The KB pistons' utilization of the permanent mold with multiple die parts allows undercut areas above the pin hole and material distribution in the skirt area that stiffen the entire piston unit. The forged piston requires thick skirts to achieve comparable piston rigidity. A rigid piston rocks less in the cylinder and improves ring seal.

The forged pistons' thick skirts add weight. The design of KB pistons gives us the option to build the lightest pistons on the market.

Some current KB pistons are not super light for several reasons. If the piston is to be used as a stock replacement, more than a 10% weight reduction will mandate that the engine be re-balanced.

Common sense suggests that the introduction of a new product be extra strong at the initial release. As the product becomes accepted, weight reductions are scheduled as regular product upgrades, as justified with actual race testing.

There will always be a market for custom forged pistons. Small runs of forgings are more economical than small runs of permanent mold pistons because of the complexity of permanent mold tooling. Where quantities justify, expect to see future KB pistons developed that are lighter and stronger than anything else on the market. Machined head profiles are easily changed with our CNC equipment so we will stay current with new cylinder head developments. Volume production is expected to keep the price reasonable."

[grumpyvette]

a good example of why higher rpms and heat and cast and most hypereutectic pistons don,t play well together

[grumpyvette]

Which Mahle Piston Is Right For Your Engine?
Comparing the 4032 and 2618 forged wrought aluminum alloys
From the November, 2010 issue of Mopar Muscle




Mahle Pistons Chrysler Hemi

Unless you rebuilding an engine with little to no budget you're going to upgrade to aluminum forged pistons. Besides being stronger than cast pistons, the lighter aluminum cuts parasitic power loss. That translates into more power at the wheels.

Recently Mahle showed us that there are distinct differences between their 4032 and 2618 alloys. The choice to use one over the other depends on your project. Are you building a street/strip machine or an all out racer? Choosing the wrong one can be devastating. To better understand, we'll let MAHLE explain.

4032 is a high-silicon, low-expansion alloy. Pistons made from this alloy can be installed with tighter piston to bore clearance, resulting in a tighter seal with less noise. 4032 is a more stable alloy, so it will retain characteristics such as ring groove integrity, for longer life cycle applications. Relative to 2618, 4032 is a less ductile alloy, making it less forgiving when used with boosted and/or nitrous applications.

The majority of Mahle forged PowerPak kits are made with 4032 alloy and require no additional piston-bore clearance. Mahle pistons are perfectly engineered to allow for the proper clearances assuming normal operation. For example, Mahle pistons for a small block engine will provide proper .0025"-.0030" clearances--right from the box.

2618 is a low-silicon, high-expansion alloy that is used for extreme-duty racing applications such as NASCAR, ALMS, etc. Due to its high-expansion characteristic, this alloy is engineered with additional piston to bore clearance. At the start of a cold engine, the pistons expanding process can be heard and is commonly referred to as the "piston slap". Once the engine warms up the noise subsides as the piston expands to its running clearance. 2618 is a more ductile alloy and grants higher tolerances with higher resistance to detonation. The forgiving characteristics allow for the most extreme conditions, but longevity is eventually negotiated after countless heat cycles.


Mahle pistons are designed for specific applications with the alloy that is best suited for that particular application.
but keep in mind the better versions of forged pistons tend to have the advantage in both strength and heat tolerances

......................Piston Alloy Comparison
4032...................................................... 2618
High silicon............................................No silicon
Low expansion........................................expansion
Tighter piston-to-wall clearance................More Piston-to-wall clearance needed
Quiet Operation......................................Noise when cold
Less ductile............................................More ductile
More stable & consistent.........................Higher resistance to detonation
Longer life cycles....................................Shorter life cycles
Harder...................................................Softer

http://www.probeindustries.com/

https://www.flatlanderracing.com/trwpistonschoose.html

http://aftermarket.federalmogul.com/en- ... 7ibJ7FwU4M

http://www.jepistons.com/

http://www.venolia.com/

http://www.wiseco.com/

http://www.trickflow.com/search.asp?Ntt ... wordSearch

http://www.flatlanderracing.com/manleypis-chevy03.html

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

http://www.ariaspistons.com/

https://www.uempistons.com/

[grumpyvette]

EngineLabs: PowerPak pistons are made from either 4032 or 2618 aluminum alloy. Please explain the pros and cons of each alloy and why certain applications get the 2618?

McFarland: These two alloys are similar in many respects. In terms of overall strength the 2618 edges 4032 out by a small margin. Silicon content makes up the main effective difference with the 4032 alloy containing 12-13 percent silicon compared to 2618 alloy having 0.2 percent or less. Silicon reduces heat expansion, while being hard increases wear resistance. The decrease in expansion allows for tighter clearances, reduced wear on both the piston and bore, also resulting in quieter operation. The hard silicon element greatly helps to increase the number of heat cycles the piston can endure before ring grooves and skirts start to distort. This makes the 4032 alloy well suited for a wide range of applications from street performance to upper level sportsman racing. The 2618 alloy is more malleable, allowing it to flex and move under extreme loads further and more frequently before reaching the point of fracture. This gives the 2618 alloy a greater resistance to the shock loads of detonation. The compromise is that the alloy softens at a much faster rate, allowing the piston to distort more rapidly. This makes the 2618 alloy best suited for extreme-duty race applications where the engine will be serviced on a regular schedule. Mahle uses the 2618 alloy for extreme-duty applications or those that have a high likelihood for experiencing aggressive and or frequent detonation. Due to the increased wear resistance and longevity characteristics of the 4032 alloy, Mahle uses this alloy on a wider scale.

EngineLabs: As head designers strive for smaller combustion chambers, how does this trend affect piston design?

McFarland: For high-compression motors, there’s a definite advantage to removing the piston dome and being able to run a flattop or shallow dish. When these same heads are used in other applications, there will have to be compromises, depending on the stroke/rod configuration used and the desired compression ratio. Long stroke/short CH pistons have physical limitations to how much dish volume is available before you start to run into the top of the connecting rod. Larger volumes in the pistons also result in less available quench area.