I dont feel that octane is the issue as to whether or not to run 10.5:1 compression on an 87mm bore. The issue is there is 1.5mm (on average) less gasket between the cylinders. I have 14,000 on the same inexpensive Cometic in my car without issues. If it had been a 10:1 or 11:1 I think the situation may have been different at the power level I am at. Obviously Mikey's car has been fine since we got rid of the PE and went to the Cometic but even then it has lost a gasket.

Aaron

 

Like other members said. Stay on the 9 to 9.5. or lower. A stock block on the eclipse and galant 2.4L block 4g64, stock compression they run a 9.1 ratio. For boost is recommend a lower compression to get the best power out of the turbo. You need to change your piston to lower compression.

 

I agree with arron, the issue is not that he cant run high compression due to octane but rather that the head gaskets are going to be easy to pop from less sealing area than the 4G63 block. Buschur has ran 30+psi on 11:1. I know, i know.... That sounds like crap BUT i have one of his "10:1" which is actually 11:1 shortblocks and i ran 28psi on pumpgas with no detonation. Showing 580whp on the virtual dyno program in dynojet mode.

The best thing about high compression is the off boost torque which i must say is awsome with 11:1. I think you should stay under 10:1 for sure with a 2.4 to keep the head sealed.

 

Im getting a BUSCHUR stage 3 head O-ringed to a MAP 2.4 LONG ROD, in 10.5 compression.

O-Rings is where its at...

 

I had an o-ringed block on my last high compression stroker and popped the gasket twice. Having an o-ringed engine allowed me to still make it home.

 

@ER Interesting thoughts on the PE head gasket vs Cometic. I actually swapped from the Cometic to the PE on the advice from a few knowledgeable individuals.

My block is O-Ringed and I have some stupid expensive ARP head studs (I need to look at my build sheet as the part name/number escapes me).

I can't go backwards now but this thread does have me a little worried. I'm doing the dual catch can setup to help with crankcase pressure but beyond that and the Kiggley HLA.......anything else i can do to ensure I don't pop a gasket?