Okay so I took my block in today for machine work. I am running 81.5mm srp pistons with the top 1.5" or so filled with moroso block filler. I didn't mention the filling to SRP when I called then for the spec piston to wall clearance and they said 0.0025". The guy at the machine shop is concerned about the lack of cooling at the top of the cylinder and recommended a little looser fit. What do you guys think? Endyn's site says 27 to 28 thou but that is probably with his pistons and the srp's have more silicon and expand less. Discuss.

 

i'd personally go 30..... 25 is way to tight

 

I'd like to know as well, as I pretty much have the same setup.

 

describe your fill procedure a bit better please.

the top inch or so is the most critical for cooling purposes. as long as you left room above the concrete before the deck height, i don't see why it'd need to be any different than SRP's spec. keeping in mind that adequate cooling will ALWAYS be in effect. the block filler holds temps, i'd be more worried about the oil temp than the temp affecting the piston ring expansion. whats a couple degrees when the top of a piston sees over 1500 degrees!

 

I agree with Josh. Actually I learned the hard way. I ran Endyn Rollerwave pistons at their spec in a fully built, balanced blueprinted and WELL tuned motor... Ran.0032 JUST like Endyn said... This is what I ended up with:




PISTON TO WALL PWn4G3

Go bigger (regardless of manufacturer). Depending on power goals, Id say .001 bigger if aiming for north of 500 WHP. Im running CPs this time around at .0045 (spec is .0035) its a liiiiitle noisy when cold, but sounds perfectly fine when warm. My machinist didnt want to run Endyns spec and I insisted. Now, I have a 640 dollar set of ashtrays.

I beat the ---- out of this motor, and its got about 6500 on the clock, doesnt smoke 1 bit and pulls like a raped Ox

 

Word to slappy pistons. My ---- was something like .0045 too and even though it slaps all the time (you can even hear it some when hot) it runs well even for being untuned. Now.. I have oil all over the place coming out from under the valve cover... but that's an entirely different issue.

 

It's a pretty standard procedure, look in the how to post and it is exactly like that. Decided to go with .0035.

 

ive got the SRP setup as well
81.00 3.189 STD 3.047 5.290 1.181 42.7 9.0:1 -2.2 281 T 149214 JXC0F4-3189-3
yeah it slaps in the cold and on start up but like he said once they heat up completely you bearely hear them, does burn a little oil tho, but i just go thicker on the grade and it doesn't eat as much