legacycentral bbs

hey all, im running 96LGT 25D heads on my car and traded a transmission for a set of complete TT 20h heads.


should i keep the 25D heads on and just swap the 20h cam's into my motor or should i swap the 20h heads on complete?

will it drop my compression ratio?

thanks, Andy

Personally I'd just swap cams, assuming they work.

If they are '96 (only) LGT heads the cams should be HLAs under-the-buckets. They should be a straight swap from the EJ20h.

When thinking about swapping the complete heads, there might be a difference in the chamber volume, with the LGT heads being slightly larger.

ok, i just did some looking. sorry for the stupid question common stuff that i forgot and should of known by now sense ive been on this forum long enough. lol


25D heads 46.6cc

20h heads 49cc

ill just swap the cam's over.

so my new added parts to my engine will be:

Garrett T350 turbo, Tial 44mm wastegate, modded sti injectors, possibly a Bosch 044 pump. and tune

The 96 EJ25D heads are 53cc, the 97-99 25D heads are 46cc. If you are sure your heads are 1996 25D, i would try to find a set of 97-99 heads. The comp ratio with the stock 22T pistons/46cc 25D heads is about 7.6:1, which is still pretty low. Definatly keep those cams, i have the same ones in my 22T/25D hybrid, and im making about 290whp on 17psi with a Rob tuned 20G ecu. The comp ratio will be below that with the 20H heads, but would work if 97-99 heads arent availible to you.
Let me know if i can answer any other questions for you on this!
Mike

ah damn, didnt know they changed the cc size in the newer years. so my comp ratio will be lower if i use the 20h heads even though they have a smaller combustion chamber?


my 25D heads are shimless bucket, pulled them from a LGT from the junkyard.

thank you for the help,andy

no, it will be higher then it is now if you use the 20h heads, since you have the shim under bucket 25d heads.

92ss satinsvoice wrote:my 25D heads are shimless bucket, pulled them from a LGT from the junkyard.

Technically, yes "shimless" buckets. You don't see shims because there are hydraulic lash adjusters hidden unde the buckets. The same as early WRX EJ20Gs and EJ20Hs.

oh shoot! if it will be higher with the 20H heads ill just swap the heads over. plus didnt the ej20H have a 7k red line?

plus the valve train is probley better too.

MikeyMeyagi wrote:The 96 EJ25D heads are 53cc, the 97-99 25D heads are 46cc. If you are sure your heads are 1996 25D, i would try to find a set of 97-99 heads. The comp ratio with the stock 22T pistons/46cc 25D heads is about 7.6:1, which is still pretty low. Definatly keep those cams, i have the same ones in my 22T/25D hybrid, and im making about 290whp on 17psi with a Rob tuned 20G ecu. The comp ratio will be below that with the 20H heads, but would work if 97-99 heads arent availible to you.
Let me know if i can answer any other questions for you on this!
Mike

you have phase 1 dohc heads right? what head gasket?
what did you figure your CR to be?

well, im running forged wiseco pistons that are 8.5 comp if i use the stock heads. im using stock ej22 head gaskets.

my compression i have no idea where im at.