New 2.5 short block

[CarpenterAWD]

I have a 97 Legacy GT and the engine is blown. In a different thread Wiscon Mark told me to go for the STI short block to fix it. I didn't really want to go with the STI because the low compression pistons would slow me down. I found a new N/A 2.5 block and I was thinking of buying that so that my car will stay relatively the same as it was pre- death to engine. My question after all of this is does the 2.5 N/A short block bolt directly up to my 97 2.5L head or is there modification needed? Do you think that it better for me to go with the regular 2.5 block instead of an STI one?
Thanks again,
Cary

[AussieDan]

If you want to stay N/A you'll need to get another phase 1 ej25 block.

The phase 2 ej25 block will bolt up but you'll have a higher compression ratio due to the lower piston volume, so you'd need a custom tune to make it work.

[CarpenterAWD]

what would i need to do if i got the sti block? what tuning would i need for the n/a engine and how much would that cost.

[blackgtbeauty]

same thing with me, but i have now a phase 2 block with DOHC's in mine and they didn't tune it.

[CarpenterAWD]

So what did you do? What happened because it wasn't tuned.

[Huffer]

You can run it (a phase 2) with mated DOHC heads. You will end up having to run higher octane to prevent detonation though.

I have a wee project engine sitting in the garage that has the heads and the phase 2 "SOHC" shortie. I actually want to get rid of it, hahaha.

[jey]

An STi block will behave kind of strange without a turbo setup since it has such a low compression ratio. You'll get lots of torque :lol: You'll want to turbo it if you get the STi block - here's what I had to get: WRX turbo, full exhaust, intercooler, engine crossmember, S-AFC, and a couple custom pipes (intake at the turbo, midpipe exhaust). Budget-turbo-swap :) Stock-like reliability - though it has it's minor quirks like most swaps :)

If you get the Phase 2 block you might be able to get by with just running higher octane fuel - though the proper thing to do is to get an S-AFC (piggyback fuel computer) and get it on a dyno and tuned.

[Wiscon_Mark]

An STi block will behave kind of strange without a turbo setup since it has such a low compression ratio. You'll get lots of torque :lol: You'll want to turbo it if you get the STi block - here's what I had to get: WRX turbo, full exhaust, intercooler, engine crossmember, S-AFC, and a couple custom pipes (intake at the turbo, midpipe exhaust). Budget-turbo-swap :) Stock-like reliability - though it has it's minor quirks like most swaps :)

If you get the Phase 2 block you might be able to get by with just running higher octane fuel - though the proper thing to do is to get an S-AFC (piggyback fuel computer) and get it on a dyno and tuned.

What if you used the EJ25 heads? Will it still be a different compression?

[jey]

An STi block will behave kind of strange without a turbo setup since it has such a low compression ratio. You'll get lots of torque :lol: You'll want to turbo it if you get the STi block - here's what I had to get: WRX turbo, full exhaust, intercooler, engine crossmember, S-AFC, and a couple custom pipes (intake at the turbo, midpipe exhaust). Budget-turbo-swap :) Stock-like reliability - though it has it's minor quirks like most swaps :)

If you get the Phase 2 block you might be able to get by with just running higher octane fuel - though the proper thing to do is to get an S-AFC (piggyback fuel computer) and get it on a dyno and tuned.

What if you used the EJ25 heads? Will it still be a different compression?

This should answer most of your questions about compression:

http://wac.addr.com/auto/obs/turbo/ejcalcs.html

[ooberdoob]

oh lord do not get a WRX turbo if you get the sti block, it's too small!

der, get an STi or just spring for a deadbolt turbo.