I dont post on here too much but, I just wanted to see what everyones Piston to wall clearance and ring end gaps were for your high hp motors.

I am building a motor pretty soon with with a 94mm crank for my EVO 9.

On my drag car I have .006 piston to wall with .030 top and second ring gap, and .016 for the oil rails and expander (Not a Mitsu, my subaru)

Whats everyone else running?


Why you may ask: I am the Sport Compact Salesman at JE Pistons and Im gathering some information.

 

The race car with the new engine im finishing for NHRA Sport Compact Race in 3.5 weeks.

 

Then why not visit the website of a firmly established competitor in this application, and download their individual piston and rings installation instructions?

http://www.rosspistons.com/

 

...

 

I know what manufacturer recommendations are, I want to know what you guys are doing.

 

im by no means a full time engine builder, but you could def say ive built a couple high hp motors.

since bore size, NA or boosted motors, and other various factors into play, a lot of different motors will run different ring end gap (im sure you know this)

but i always make the second ring a tad bigger.

on my current project evo build. Im deciding if i want to follow JUN's recommendations of .05-.07mm ( which is .0019" - 0.0027") for the piston to wall clearance. it seems a little tight. i might go with the looser side...

I think what it really comes down to is the thermal coefficient of expansion , heat causes expansion. you have to ask, what is the motor is going to be built for. the looser, the better for big power, but most likely wont last as long as a tighter motor.

 

Mase where did you get JUN's recommendations on piston to wall?

 

I am building a 2.3L stroker for my evo and I am goign to use the .006 clearance. I am not too sure yet for the ring gap. However, that gap is also from the je pistons. That is because thats how je makes them unless you ask them to make them differently.

 

We dont make the rings. We have pro seal rings which are all file to fit. There is a general guideline to the minimum ring gaps. Call me at JE if you need more info.

Ask for Nick

 

From Mr. Takahashi @ JUN

but remember its application specific for the most part, everyone shouldnt run their recommendations, as each piston can vary.

 

which is exactly why I found a specific recommendation without other-factor list curious