Headgasket Questions

smh0101 · Post by **smh0101** » Sun Nov 02, 2008 10:57 pm

So, if I were say gonna use an ej257 shortblock... with 93-96 jdm WRX ej20g heads... what headgaskets should I use? STI 2.5L headgaskets? 2.2T headgaskets? or what?

If I used a built 2.2L short block I'd use the 2.2t Gaskets... but if I used an STI shortblock, should I use STI headgaskets?

555BCTurbo · Post by **555BCTurbo** » Sun Nov 02, 2008 11:10 pm

Always use head gaskets that match the block

smh0101 · Post by **smh0101** » Sun Nov 02, 2008 11:31 pm

Kewl, thanks Nick... I wasnt sure if I should use the gaskets that match the block or the heads... if it were the heads, that would be more of a problem lol... bcuz the heads... are JDM

555BCTurbo · Post by **555BCTurbo** » Sun Nov 02, 2008 11:35 pm

Yeah...those heads actually have the same coolant and oil passage layout as the 2.2 sohc, WRX, etc. I would venture a guess that their original factory spec gaskets are the same as 2.2t ones.

smh0101 · Post by **smh0101** » Sun Nov 02, 2008 11:49 pm

Huh, well thats interesting...

Would I have any problems coolant passage wise with a 257 shortblock and those WRX heads?

Aerotech · Post by **Aerotech** » Mon Nov 03, 2008 3:25 am

None at all... that's basically the setup I'm running, but with JDM Legacy heads.

smh0101 · Post by **smh0101** » Mon Nov 03, 2008 4:18 am

See, I have brand new OEM Subaru Bearings, Rods, and Pistons... They were assembled in a crate motor... then the guy had Bearing Services take the crank and block and rebuild it with fully forged internals... then sold the rest of the stuff to me for $50...

And up in Tacoma there are 257 block halves and crankshaft for $300...

So for a total of about $350 I could have a stock STi Shortblock...

And I already have the heads, intake manifold, injectors, wiring, and turbo for stage one of my build...

And I dont plan on using any turbo larger than a vf43... maybe eventually a JDM twinscroll or something, but nothing too big.

Basically the plan is to build the motor with a vf10 turbo and 440s, then, once I get EM, switch to a vf43 and 565s.

I know that with that build I dont necessarily need wisecos, and it'll have more torque even than my 2.35 that I was planning... and it wont be a franken-block with ej25d parts.

And seeing what Devan and Dale have done with that stock 257 block kinda made me reconsider its use... 327hp at the wheels with 16lbs of boost, nice... so what could that motor do with 20lbs and a link

(And I know I'm using older heads... but my heads a similar to what Dave is using, which is making more power than Devans car)

So thats where I'm leaning right now.

555BCTurbo · Post by **555BCTurbo** » Mon Nov 03, 2008 4:38 am

Talk to Barrett Dash about this...he built exactly such an engine...with a VF8

Matt Monson · Post by **Matt Monson** » Mon Nov 03, 2008 4:50 pm

Cometic, and a couple of other companies, have been making gaskets for the Ej257 that are ever so slightly thicker than a stock STi gasket. The reason for this is that the Ej205 heads have a smaller combustion chamber than the Ej257 heads because of the bore differential between the two engines. The slightly thicker gasket keeps you closer to the stock compression ratio and less prone to detonation. If I was building one of these engines I would use that head gasket with the JDM Ej20 heads.

93forestpearl · Post by **93forestpearl** » Mon Nov 03, 2008 6:02 pm

Cometic does make them with the 98mm bore. I have a set I'll be using with the .051 thickness when I put the 25D heads on. Cometic makes those per order so expect up to a 2 week wait.

Matt Monson · Post by **Matt Monson** » Mon Nov 03, 2008 11:37 pm

http://www.flatironstuning.com/shop/pc- ... ej257.aspx

They are in stock on the Cosworth version. No waiting.

93forestpearl · Post by **93forestpearl** » Tue Nov 04, 2008 2:16 am

I only see 93mm and 101mm bores, and damn are they expensive. I paid $75 for my Cometics.

Aerotech · Post by **Aerotech** » Tue Nov 04, 2008 3:28 am

That's about right... per gasket. I bought one from E-bay last year and was shocked to find only one in the package

Cheap compared to yanking the motor to re-do a head gaket job, though!

93forestpearl · Post by **93forestpearl** » Tue Nov 04, 2008 3:32 am

No, $75 for the pair. If you pay over $95 for a pair of Cometics you fail at google.

http://www.sportcompactonly.com/Subaru/ ... 5_m-26.htm

http://www.rallysportdirect.com/shop/co ... -2425.html

smh0101 · Post by **smh0101** » Tue Nov 04, 2008 3:35 am

Epic FAIL... LOL JK... that was just a random thing... not aimed at anyone... lol

So what thickness would I want? if i was gonna go with say the cosworth ones?

93forestpearl · Post by **93forestpearl** » Tue Nov 04, 2008 3:40 am

That's a tough call, because the 101mm bore gaskets will be set back a little bit, but not the end of the world. The trouble lies in the fact that the EJ22T pistons protrude beyond the deck by a hair under .020. I could see if .040 gaskets would clear, but I'd rather not trash a set to find out, so I'm going to use the .051 set.

Maybe this summer I'll see if the old 22E block I have laying around protrudes by the same amount and I can sacrifice one gasket and some beeswax to see if there is enough clearance. I would like to be above a 8.0:1 compression ratio (slightly).

93forestpearl · Post by **93forestpearl** » Tue Nov 04, 2008 3:42 am

Oh, wait, you are planning on a 257 shortblock. Nevermind.

You should be able to get the .040 cometics right away, or use the OEM MLS gasket just fine.

I was just talking about the 98mm bore .051 thickness gaskets, since Cometic does not sell many and therefore does not stock them. If you go with the 257 shortblock, you should have no trouble finding decent headgaskets in short order. IIRC, the factory MLS gaskets are actually quite decent.

smh0101 · Post by **smh0101** » Tue Nov 04, 2008 3:42 am

Do the ej257 pistons protrude from the block like that? because I'm talking about using a ej257 short block 2nd gen ej20g WRX heads combination...

smh0101 · Post by **smh0101** » Tue Nov 04, 2008 3:44 am

I remember Davey having issues with his built 2.2t block with STI headgaskets and ej25d heads... the gaskets were too thin and ever so slightly tapping the valves.

93forestpearl · Post by **93forestpearl** » Tue Nov 04, 2008 3:46 am

smh0101 wrote:Do the ej257 pistons protrude from the block like that? because I'm talking about using a ej257 short block 2nd gen ej20g WRX heads combination...

I'm pretty sure they do not, thus running the thinner (.040 IIRC) gasket from the factory. The 22T gasket is about .059 OEM.

Aerotech · Post by **Aerotech** » Tue Nov 04, 2008 4:09 am

I can confirm that... I'm running 0.040 Cometics on a EJ257 / RS-RA head combo.

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Headgasket Questions

Headgasket Questions