Generally on a hp build with a subaru you want ~30-40 thou from the head to the top of the piston, so if your using a 0.8mm(~.030") gasket your deck height should be 0....or 10 thou down the bore for an engine that will rev past 9k

I haven't used that piston and rod(but on the face of it that should work fine in a EJ) but if its the case that your deck height is +.020"(thats why its touching the head when it rocks in the bore) you may be able to solve things with a 1.6mm gasket....should be fine for ~500hp and 8k rpm.

If your deck height is +.030" thats unusual ....something may have gone wrong with machining etc....you can get thick gaskets but they aren't the best.

You sure its the piston hitting head ? not a valve ? is cam belt on ?

You need to measure deck height and work out whats going on.... who did the machining and the rest of the clearances etc ? what were the big ends set at ?

__________________
MY99 WRX EJ2.35L 720whp 9.48@147mph
https://youtu.be/c_lYEG0_Dyo

I'm not too sure what the big ends were set to as my mate did the reassembly while I've been away with work...

Ahh shit....i just goggle that rod...thats an old EJ25 NA rod....131.5mm, 1mm to long to use with that piston !

Machine 1mm off the piston tops is your best way out, seen it done before when replacing pistons in a JUN or Cosworth stroker kit.
Whoever specced the parts list ...and the machinists fucked up.


You still need to measure deck hieght...before you disassemble would be good then you can take the correct amount off the piston top to use a thin gasket. Then measure deck hieght again when re-assembled to check

__________________
MY99 WRX EJ2.35L 720whp 9.48@147mph
https://youtu.be/c_lYEG0_Dyo

If that's the case I'll just get a new set of rods that are the correct ones, but I'll wait till the motors apart again and have measured everything up just to make sure...

There's no problem taking 1mm off piston....and a longer rod is always better

Would only be like $60-80 to have a machine shop take some off pistons.

__________________
MY99 WRX EJ2.35L 720whp 9.48@147mph
https://youtu.be/c_lYEG0_Dyo

What are the pros and cons of doing this?

Pro's:

Cheap
Easy to remove pistons without disassembling short.
Longer rods in a 2.5 make ratio better(bearing speeds, angles, dwell)....some say 1mm won't make sfa difference, some like to believe !(Cosworth and JUN did !)

Con's:

Don't think there are any really....won't weaken piston taking 1mm off top ridge...

__________________
MY99 WRX EJ2.35L 720whp 9.48@147mph
https://youtu.be/c_lYEG0_Dyo

I'll update with the outcome of what the problem was once it's all been checked out, so in just over a weeks time...


Cheers for all your info guys it's been much appreciated and I've actually learnt more about my cars engine!!

Or a shorter crank eg. 75mm from a EJ207

Cheers for all the info guys!

Engine is stripped apart again, and the rod lengths are to blame!!

all machine work is within tolerance as far as we can tell...