EJ255 block with EJ22T heads or '96 EJ25D heads

[wtdash]

Hi,

Since my 'new to me' '96 Legacy L - EJ22 - is very similar to the 1st Gen, hopefully some Gear Heads can chime in.

EDIT: Filled in what I found w/this LINK w/CRs. Includes HG thickness.

Looking for Compression Ratio for the following setups:

- Thin (0.56 mm) vs. Thick (1.37 mm) HG CR's added

EJ257 block* + EJ22T heads + STi HG = 9.6 / 9.0

EJ257+ '96 EJ25D (HLA) + STi HG = 8.9/ 8.3 (estimated as '96 was 9.5:1 vs. '97-'99 9.7:1 STOCK CR)
>>>>>>>>>>>>>>>>>>>>>>>8.5 estimate w/comparable EJ20H heads (DOHC HLA, stock 2.0 HG)

EJ257 + '91 EJ22e heads + STi HG = 9.6 / 9.0 (estimated based on EJ22T head CR)

I DO NOT WANT TO DEAL WITH EM - No Wiring, thanks. Yes, I'd like to run 5 PSI w/a VF11 on the 1st setup, since it's already plumbed. But not sure I want to deal w/all the extra work....and potential for more issues.

Thanks


*Actually an '09 EJ255, but has new STi pistons, so w/STi heads stock CR is 8.2:1.

Notes from HERE:

Use the 11044AA610 gaskets. Do NOT use the 642/670/770 gaskets as the pistons will hit the cylinder head at TDC.

I hate to give up that much CR, but also don't want to spend 2X on getting too thin of a HG.

[mike-tracy]

I'm gonna say the 96 ej25d is the ideal combo of what you listed. Primarily because the combustion chamber matches the bore of the ej25. What are the CR's? No idea without punching a lot of numbers into an online CR calculator

[wtdash]

Fire up a CR calculator or wait for someone who will for you

well...that's why I'm asking. CR Calcs =

Good LINK

[mike-tracy]

Nice link. For that 25d I'd use the legacy ej20 column.

[cj91legss]

This compression calculator is what I used when figuring out which head gaskets to use for my hybrid.

https://www.google.com/url?sa=t&rct=j&q ... 7601,d.bGg

Lonk link But it's TWE Compression Calculator. It's a direct link to download the excel file.

[86BRATMAN]

96 heads will be the best match for an ej257 shortblock. They have the same combustion chamber volume as the b25 heads @ 56cc. With sti head gaskets you'll be at stock ej257 compression ratio.

While the b4et chart is a decent reference, there are several wrong entries in it. The 96 ej25d heads are one of them.

[Alphius]

I was going to chime in and say that TWE sheet has several glaring inaccuracies. The 96 EJ25D heads will indeed result in the lowest CR.

[cj91legss]

Gabe, maybe you could get with me and check it out then because my motor doesn't feel like a 7.6:1 compression engine.

[Alphius]

CJ, what HG did you use?
I get around 7.7:1 with EJ22T pistons, .8MM MLS headgaskets and EJ205 heads.
Around 7.3:1 with thick EJ22T sized gaskets.

wtdash, EJ257 block with 96 EJ25D heads should make 8.2:1 CR with stock STI HG part number 11044AA642. This is really the only safe 5psi turbo setup.
With your other EJ22 head combos it will make 9.9:1 CR which would make for a sprightly N/A engine with EJ22 heads, but likely not boost friendly without EM. Not as much CR and not as much power as your standard EJ22/EJ25 frankenmotor, but should be bulletproof for obvious reasons.

[cj91legss]

Cometic 1.3mm

[Alphius]

7.4:1

Good quench distance with that HG and the EJ22T piston deck height.