I have posted this before, but i dropped off my block today, and wanted to know what you guys thought about my projected clearances.

I have SRP 4032 high silicon alloy pistons. the spec sheet says:

d16z turbo about 12psi (intercooled)

.0022 - .0028 +.001-.003 (for turbo)

i was thinking or running .0030" for my piston to wall clearance. let me know ASAP. thanks.

 

I'm running about .0020 on cast pistons so I would think that the high silicon content of your pistons will expand nicely. you may have some knocking sounds until warmup. I would call the manufacturer they would know best.

good luck

 

it was my understanding that the silicon allows for tighter clearances bc it DOESNT expand like stock pistons. anyone with srp's installed?

 

hmmm, I did my wiseco at .0035, and I believe the wiseco and the SRP's has similar contents of silicone. piston slaps for the first 30 secs at startup then it's gone


stan

 

stock cast pistons only requires .0001 skirt to wall clearance...they hardly expand at all...

 

so my SRPs will expand more than stock pistons?

 

yes, absolutely

 

so what is the purpose of the silicon pistons just the fact they are forged and stronger?

 

High silicon content allows you to run a tighter piston-to-wall clearance because the piston will not expand as much. Tighter clearance is beneficial to ring life and reduces noise.

However, high silicon content also makes the piston more brittle. Most aftermarket forged pistons contain low amounts of silicon (compared to stock pistons). However, they require more clearance and make more noise.

The SRP's have more silicon than JE's/Wiseco/Arias/etc pistons. You should be able to run tighter clearances than what you listed. Give JE a call and get some input from them.

Sonny

 

I went .0032 or .0034 on my JE's---i forget which I get a decent amount of knock until the car is well warmed up, talking like 140 degrees. Went loose on all clearances cause I will eventually try to see how much my dartons will take. I will someday boost 30+ for the hell of it. Actually I went loose cause I will eventually run no2 and high boost.

 

it sound like with my mild boosting 12psi-14psi (MAX) that my .0030 would be ok. I dont want to go too loose and get alot of slap, or too tight and ruin my sleeves. I know JE and SRPs are simliar. thanks for the input. anyoenelse?

 

.003-.0035" seems to be the going clearance for forged pistons in turbo applications. My Arias pistons calls for .003" piston to wall clearance for turbo apps and .002" for all motor.

 

after talking with SRP and hearing what you guys had to say. I went with .003"

SRP also suggested the recomened gap for my rings. (my pistons are .01 oversized)

top ring .017
second .014-.015
oil rings -just put them in- (should be > or = .015)

 

Not true, only the h22a(and other variants) to my knowledge use such tight clearances.
The b18c uses .0006-.0014" for example.

 

The spec sheet for my custom JE's were .0038" of clearance.

I'm going to be running about 25psi of boost....

is this just right, to much, to little ect...
Thanks

 

.0038 is a shitload of clearance.

General rule for forged pistons is .001 for every inch of bore. Mine are at .0030 using Endyn/Wiseco pistons on a 75.5mm bore (2.972 inches). Do whatever the piston manufacturer recommends.

AFA the SRP's, you should be able to run tighter clearances since they don't expand as much. One of the SRP selling points is that they are quiet. They aren't gonna be quiet if you run them at .0030".

Sonny

 

i will be able to post how it sounds when running after i get it put back together.

I spoke directly to the SRP tech. and 2 machien shops who build these kind of engines, they suggested .003 as my piston to wall clearance.

like i said i will let everyone know how it goes together and sound after the build.