compression ratios?

asc_up · Post by **asc_up** » Mon Oct 02, 2006 7:18 am

So anyways i'm trying to get my 2.2L n/a up to 150 chp so i was thinking about doing a head swap and putting the 2.5 heads on.

I asked a subaru shop around here and the guy said i would lose compression and it wouldn't work as well.

is this true?

entirelyturbo · Post by **entirelyturbo** » Mon Oct 02, 2006 4:02 pm

Sure is. Head volume of the EJ25 heads is larger.

You could get the worst-flowing heads of the entire EJ line, the EJ18 heads off an early 1.8 Impreza. That would up your CR, but I don't know how much. No one has measured the head volume of EJ18 heads, but I plan to do it sometime in the near future.

If you desperately want to have a higher CR, you could have custom pistons made and have your heads milled a tiny bit.

But if you want N/A power, the best thing to do would be to have headwork done, cams reground, a little extra fuel, and some halfway-decent engine management. PM Matt Monson, he just recently did this with an EJ22.

asc_up · Post by **asc_up** » Mon Oct 02, 2006 10:48 pm

so if i put the 2.5L heads on it will actually decrease my hp?

Matt Monson · Post by **Matt Monson** » Mon Oct 02, 2006 11:07 pm

If you put the Ej25 heads on your engine, it will probably be about a wash. You will be trading lower compression ratio for increased flow.

A more appropriate approach for NA HP would be to put an Ej25 shortblock against your stock heads. That will bump your CR a fair bit, in addition to upping your displacement at the same time.

Then, get a set of cams from Delta, which run about $175. It won't get you anywhere near your desired 150chp, but it will make a big difference over stock. It depends on what dyno you run it on, but I would guess you will be around 190-200 Chp...

asc_up · Post by **asc_up** » Tue Oct 03, 2006 6:13 am

ok cool.
any idea what the whp would be?

and where might i find the 2.5 short block? like a website or just a junkyard?

Project_Legacy · Post by **Project_Legacy** » Wed Oct 04, 2006 6:13 am

junkyard would be a good one. i think they made them from 97 and on? your in washington? east or west of the mountains?

asc_up · Post by **asc_up** » Thu Oct 05, 2006 12:06 am

Project_Legacy · Post by **Project_Legacy** » Thu Oct 05, 2006 3:54 am

the roy y junkyard may be a good one to check out, if you are near there, thats around the tacoma/spanaway area.

asc_up · Post by **asc_up** » Thu Oct 05, 2006 5:16 am

hmmm ok then...
i'm in university place.
how much do you think they would charge me for it?

Project_Legacy · Post by **Project_Legacy** » Thu Oct 05, 2006 6:45 am

not too sure, but i did pick up a 94 ej22t for $550 bout 1 and a half years ago. most likely you will have to buy the whole 2.5 longblock, i would say around $700 maybe depending on mileage?

asc_up · Post by **asc_up** » Thu Oct 05, 2006 7:28 am

hmmm ok.
but i just need the short block right?

Project_Legacy · Post by **Project_Legacy** » Thu Oct 05, 2006 7:36 am

that sounds like what they were saying.

you can even resell those heads you get if u wanted to.

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compression ratios?

compression ratios?