head mod's for 2.5
 

has anybody on here mod'ed their cylinder heads to suit the bigger bore of the ej257?

if so what needs doing and do you have any pics?

thanks

use the same heads mate as far as i know

thought they were diffrent:wonder: think you have to get the combusion chamber machined .

Lots of people run standard EJ20 heads (normaly upgrade to STI) on 2.5 conversions, i had the bores increased on my old car to match the bore of the 2.5 block.

yeah they are sti v5 heads i have, but i read somewhere that it helps to machine them to the size of the bores.

did you find any difference after the machining of them?

also what did you do to them? did you jut enlarge the area around the valves to the size of the bore?

there is a little bit of info in the group buy section under 2.5 block group buy.

They were done at the time the engine was built so never had them on there without it done.

I didn't do it myself the guy who built my engine took the heads to a machine shop and got them done for me, but i believe they did just enlarge the area around the outside of the valves (combustion chamber )to the size of the block bore.

thanks for that.

just looking at your scooby and i see you run meth on the one map. i was thinking about doin this as i'm going down the simtek route.
two things, where do you get the meth's from and is it worth it, can you feel a big difference when on the other map?

thanks.

The Meth Map is at higher boost aswell so was a massive differnce on my old car, i got it from a localish guy who used it to make bio-diesel and always had plenty he didn't mind selling on.
Personnally if i was going down that route again i would probably go for 20% Bio-Ethanol instead as it easier to get hold of (some Morrisons sell it at the pumps) more info: https://www.scoobynet.com/general-te...ioethanol.html

On my second 2.5 build, both used sti V heads untouched.

first one achieved 452bhp @ 1.4bar on a GT30R hoping for near 600 on my current build.

You don't have to have the heads machined you can simply use a thicker head gasket. Using a pair of 1.6mm gaskets will give roughly the same compression ratio.

Gaskets are available from all the usual suspects RCMS, Lateral Zen etc.

It also depends on the piston that you use as i've been told that you can get custom EJ275 pistons to suit the 2L heads.

My RCMS Omega's are a low comp piston, these when paired with a 1.6mm gasket result in an 8.35:1 CR