I recently ordered my rotating assembly. I ordered the JE pistons #131636, these are -22 dish. They are the biggest dish JE makes for 5.7 rods and a 3.48 stroke. I'm running 62cc heads, and these pistons are advertised at 8.7:1 compession with 64cc heads.

I was just looking around, came across JEs web site, and noticed that they had a link to SRP pistons. Are these the same company or what? Anyhow, i noticed SRP has part #139632, this is a -24 dish. Going by Summit racings prices, they are 125 bucks cheaper, and lower compression ratio to 8.5:1 with 64cc heads.

I figure with the first pistons mentioned, the JEs, i'm going to be around 8.9:1. And with the second ones, 8.7:1. How crucial are these couple of points in compression? I can probly make up the 2ccs of dish in the thickness of the head gasket but i also hear people have problems when they go too thick.


I guess my questions is... is one piston stronger or more reliable then the other? (both are forged aluminum) If not, why not save the 125 bucks and get the lower compression?

BTW: i'll be running forged h beam connecting rods (5.700), with a forged scat crank. Going to have a t76 front mounted, intercooled turbo set up.

Anyone?

 

The difference is in the forging. JEs are 2618 material and SRPs are 4034. Simply put, the JEs (extreme duty) are designed for high boost applications. They are heavier (more material for heat dissipation), and the 2618 material is more durable. The drawback to the JEs (2618) is that they require looser clearances for expansion purposes so this may increase oil consumption and make for noisier start-ups. Some people make it fine with the SRPs but I went with the JEs in my build for piece of mind.

"There are two common alloys used in forged pistons, 4032 and 2618. Silicon-aluminum alloys, such as 4032, have great wear characteristics because the silicon particulate hardens the alloy and reduces the thermal coefficient of expansion. However, silicon-aluminum alloys can turn brittle and become prone to fracturing when subjected to extreme stress. With a piston made of a silicon alloy once a crack starts, it doesn't stop until the piston suffers a catastrophic failure. Low- or no-silicon alloys, such as 2618, may wear a bit faster but provide better strength and durability. In the rare case of a crack in a 2618 piston, the crack will migrate to an area of lower stress and stop. 2618-alloy pistons keep their shape under extreme pressures and high RPM's."

As far as blok prep; zero deck the block and use an .040 gasket. What's your CR? No big deal between 8.7 vs 8.9 CR.

 

When you say require looser clearances for expansion. Should i be concerned about this when boring the block? Or are these clearances already in the piston it self allowing it to expand?

With these looser clearances, is blow by a problem considering the high boost. I would assume any issues like that would go away once everything is up to temperature.

What head gasket are most guys running? I plan on running 12-15 pounds of boost.

 

The pistons ordered need to be sized correctly. When you order the pistons, just tell them the overbore you have. The 2618s tend to consume a bit more oil but I've not noticed anything significant. For gaskets, most people go with a FelPro 1074 or Cometic. Cometics are more "bullet-proof" but require a very fine surface finish to seal properly. More so than the FelPros.

 

Do NOT use SRP's for boost! They won't melt, they shatter with a little detonation and take out your brand new block etc. Don't ask me how I know.
Seriously, the 2618 is much stronger and better suited for boost. The SRP's are great nat. asp. but will not tolerate det.
Steve

 

im thinkin its gunna be fairly hard to get my compression down into the 8's with stock lt1 heads

 

Diamonds!!!

 

my solution to you would be:

get it tuned right and it wont detonate

i ran srps in my honda (making 441hq/362tq) for ~2.5 yrs,
i beat the crap out of it daily,
tons of hot laps and they held up good. finally blew them racing a new vette

yes there are better pistons out there, but spr pistons are not junk.
imo

 

Have run SRPs for 2 season widhout problems (19psi widh N2O)

 

DITTO!!! DO NOT use SRP for boost you will be very sorry