Well i had a chance to get some more mesurments of diff. subarus blocks and heads and hear are just a couple more.

EJ257 piston volume(the dish) is 22cc's
EJ20G Combustion Chamber is 44cc's

a member on this forum has this setup w/ a EJ257 head gasket and is running a CR of 9.23:1(can anyone say AutoX)

hope this helps someone...

kirill

I wouldn't want to be running 9.23:1 with a lot of boost on a stock EJ257. Been there done that...

Exactly what does a EJ257 head gasket have to do with anything.

It's pertinent information if you are talking about compression ratios.

I would assume the thickness of the gasket would be pertinent but not what engine it went to!!!

well i said the headgasket becouse the ej207,ej257,and ej20g are all diff. thicknesses.

and why would u run high boost w/ a car that has that high of CR(thats one reason for the high CR, so u dont have to run allot of boost)? this combo is for a solo2 car, witch means that the lag will be to a minimum.

(snowman4us)

The compression ratio buys you a little in the throttle response but it will not buy you a ton of power. You increase cylinder pressures very fast with little boost and like I said, been there, done that. Even at 14psi you are going to be pushing the longevity of the block. I'm very familiar with building a solo2 car, I trophied in SM at the 4 national events I went to last year (3 3rds and a 2nd). I'm building a new car for this year out of a GC8 body car, it should do better.

well if u have a CR of 8.0:1 and u are running 18PSI, ur CR will be at 17.8 at full boost.
if u have a CR of 9.5:1 and u are running 12PSI ur CR will be 17.3:1...

so just by looking at that, its easy to tell that the block can take more. i think as long as u stay around 15PSI it should be safe. and just think running like a VF series turbo w/ this settup. i can only imagine how AWSOME the powerband would be, im willing to bet it would have less turbo lag then a STi(usdm) would.