hey quick question, i cant really find any info on what heads i would need to use to get the compression low enough to run some booost. i have a ej25 block without any heads at the moment. just wondering what heads would be ideal to get that cr down? also where can i find some low compression pistons for it? tried google but cant really find anything.
sorry dont know too much about subarus yet its for my gf car, on the block all it says it ej25, the guy that sold her the car and the block said with the stock 2.2l heads it would make somewhere around 11:1 cr
the stock ej25 1 out of the usdm impreza should be fine on 92 for about 6-8lbs if i'm not mistaken. why would you put 2.2 heads on a 2.5? that would be restrictive. The common setup is 2.5 heads on a 2.2 block to raise airflow and compression. I could be wrong on any of these counts though?
Through my understanding putting the 2.2heads on 2.5block raises compression and putting 2.5head on 2.2block lowers compression. To back up my theory it all has to do with the gaskets and the dome of the heads. 2.2heads smaller dome, and 2.5 heads slightly larger dome. large dome small cylinder low compression. small dome large cylinder higher compression. This is only my theory. Those whose know the actual facts please shine in and correct me if i'm wrong. The most common way is to chage pistons not heads although in theory they will work.
Find out what the bore is, I have a set of STi pistons sitting in my garage. Never used. Wrist pins and such.
