Reduced compression hypereutectic pistons - Are they THE LAW?
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Reduced compression hypereutectic pistons - Are they THE LAW? If you look around at daily driver type hypereutectic pistons (like Speed Pro, Silvolite, Mahle hypereutectic, etc) for a rebuild, you can’t help but notice that they all have a lowered deck height compared to OEM pistons. The result? Unless you deck the block, mill the heads, and/or use thinner head gaskets, you WILL lose compression if you use these pistons.
I have always wondered why nobody sells stock compression height hypereutectic pistons, as these would be desirable for people who have no interest in nitrous and/or forced induction. The other day, I brought this up while taking my block to the machine shop, and he said that there is a reason why ALL hypereutectics are reduced compression height. Quite simply, he said it is a federal law. Specifically, this is done to keep compression from being easily increased during rebuilds in order to keep emissions in check. The reasoning here is that hypereutectic pistons tend to be used in vehicles that are driven more on a regular basis than forged pistons (which are often used on non-daily driven high performance vehicles). So the government targets hypereutectic pistons rather than forged pistons (which are often sold as ‘for off-road use only’). Is this true?
I have always wondered why nobody sells stock compression height hypereutectic pistons, as these would be desirable for people who have no interest in nitrous and/or forced induction. The other day, I brought this up while taking my block to the machine shop, and he said that there is a reason why ALL hypereutectics are reduced compression height. Quite simply, he said it is a federal law. Specifically, this is done to keep compression from being easily increased during rebuilds in order to keep emissions in check. The reasoning here is that hypereutectic pistons tend to be used in vehicles that are driven more on a regular basis than forged pistons (which are often used on non-daily driven high performance vehicles). So the government targets hypereutectic pistons rather than forged pistons (which are often sold as ‘for off-road use only’). Is this true?
Last edited by StorminMatt; May 2, 2018 at 03:31 AM.
Most places like that offer them for a reason. They are mainly made for rebuilders and most rebuilders will surface the block.
Having said that, i have personally installed a few sets of these pistons and on paper they show reduced ch but in realiity nearly every one has been 0 deck.
Its not a law or anything else like that, its purely due to rebuilders.
Having said that, i have personally installed a few sets of these pistons and on paper they show reduced ch but in realiity nearly every one has been 0 deck.
Its not a law or anything else like that, its purely due to rebuilders.
Quench Distance Hi Matt, my concern would be a .050"+ Squish with your Hyper piston CD ALLOWING LESS Knock resistance.
The Hyper piston material is weaker than a Forged Piston/Better than a Cast Piston as we know
Sure, the best answer is a FelPro .041" Head Gasket, closer if possible .032".
Would you fit an "offset pin" piston ?
Lance
The Hyper piston material is weaker than a Forged Piston/Better than a Cast Piston as we know
Sure, the best answer is a FelPro .041" Head Gasket, closer if possible .032".
Would you fit an "offset pin" piston ?
Lance
As a general rule, i think more compression INCREASES efficency, doesnt it ? Id be more app to believe hyper pistons are used in alot of builds that dont get blueprinted for clearances and often with parts that have had historys of muliple trips to the machine shops ie decked . So to avoid problems with backyard rebuilders throwing stuff together without measuring clearances, they just drop the crown a few .000s . Most backyard builders arent gonna notice the lower compression hight anyway. Not to offend anyone who builds their stuff in the backyard. Been there myself. Cheaper pistons are used by a wider demographic than high dollar forged stuff .
Compression Ignition Hi OLD School 72, The HEAT of compression ADDS GREATLY to the "art" of combustion !
THUS this "art" of squish distance reduction REDUCES the Spark Instant REQUIREMENT greatly, a VERY GOOD thing to spec.
Lance
THUS this "art" of squish distance reduction REDUCES the Spark Instant REQUIREMENT greatly, a VERY GOOD thing to spec.
Lance
