PII EJ25 shortblock/PII EJ22 heads frankenmotor

[wotdsm]

Hey everyone. Been lurking for a while but finally decided to post.

 

I have a 99 forester that started life with an EJ253 auto. I bought it with warped heads so I dropped a Phase 2 EJ22 into it from my OBS. I then swapped it to manual with a trans, torque tube, and LSD rear diff out of a 2.5RS. Then just recently I donated my EJ22 shortblock to my friend. We put WRX heads and accessories on it to make an EJ22 WRX hybrid build for his brother (who is also a good friend of mine), whose bugeye has been sitting in a garage since 09, as a wedding gift. We restored it behind his back. It was great...

 

Anyways, I replaced my short block with a phase 2 EJ25 and kept my phase 2 single port ej22 heads. Now I understand that the typical frankenmotor swap is a phase 1 or 2 EJ25 shortblock with phase 1 EJ22 heads that have a smaller combustion chamber than my Phase 2 EJ22 heads. The car runs great and feels very responsive and torquey, but some folks are telling me I really didn't gain anything as far as compression ratio or power other than maybe a scoch of low-end to midrange torque due to the single port.

 

tl/dr: do you get any benefit from doing a Phase II EJ25 shortblock/Phase II EJ22 single port head frankenmotor? Fel-Pro MLS headgasket used in this instance. Is compression raised at all? Do you gain torque or HP?

[bratman18]

Everything I've seen and read says the phase 2 2.5 heads and the phase 2 2.2 heads are basically the same.

[wotdsm]

That's the general consensus. The car is extremely torque-y now and runs like a dream. But, I'm used to driving it with a 2.2 as that's what it's had for the past year or so. So I'm not surprised I notice a difference. I suppose I need to line up at a stop light next to my buddy with a stock SF forester and see who's faster lol.