I decided to throw a 2.4 in my evo8. So far, I have had **** luck. It’s just your basic 03 galant 2.4 w/ stock crank, Manley Ibeans, Wiseco HD pistons 10.0:1 87.5mm. I ran a cometic 3 layer MLS head gasket and it did not last long at all. Matter of fact, it **** the bed the moment I tried turning it up past 24psi. Logging coolant pressure, it shot up and ballooned my koyo radiator and shot coolant out of the overflow on a 3rd gear pull. People were telling me you need to Oring the head but I refused to accept that as an answer for low boost especially considering I’ve ran 40-50psi on 2.0 set ups for years and had no issues. So I decided to toss an oem evo9 5 layer MLS head gasket in there. That gasket held perfectly coolant pressure perfect but it started eating plugs due to detonation probably due to the gasket edge slightly hanging in the combustion chamber. I’m now going to try a Cosworth MLS that’s a 4 layer and made for this 2.4/2.0 setup. But I’m curious what everyone has had success with.

Things to note: I have 625 head studs, head has ARP shoulder inserts, Car is tuned on flexfuel but always has E85 in it (sensor reads E74) I’m targeting 11.7 afr gas ratio scale and it’s on very safe timing (unless my base is off which I’ll check).

 

How good was the finish on the block and head? What did you torque the head studs to? Did you retorque the head studs?

 

The RA on the head was 22. The block we didn’t resurface because it looked pretty good and we checked it for flatness and found no issue. We should have just done it before I dropped it in for peace of mind but it’s whatever. The fact that the cometic didn’t hold at all and the oem did tells the story of the quality of the gasket between each other regardless of surface finish.

Head stufs torqued to 100ft lbs each time, then retorqued the next day after settling then retorque after a couple heat cycles but torqued cold. I found the numbers to shift 5ft lbs. tops on the retorque and it was only on a couple studs. This time I torqued to 105 on the cosworth gasket. I will find out how well it holds at the shootout

 

You didn't deck a junkyard block? Bold strategy cotton...

The cosmetic gasket works fine. You just put it in a no win scenario.

 

Where did I say it was a junk yard block? The block was machined and resurfaced, engine ran for about 1000miles, I bought it and went through it to make sure everything was good and reassembled it. And like I said the cometic failed almost immediately, the oem mls held like a champ so using a cometic and an oem on the same exact surface and the oem never skipping a beat tells the story that cometic gaskets are weak and need the help of a SS oring to seal properly. This is a 600hp+ car that’s actually raced, not hard parked

 

Yep, my cars are all hard parked. Good luck with your "racecar" engine that couldn't hold 24psi.

Had a car here do 800whp at 40psi with a 6466. 2.2 in a 4g64. With a cosmetic gasket and no oring.

 

I didn’t say you hard park. I just said I don’t park my car, I actually race it. Also my car holds 50psi just fine on an oem gasket only. You enjoy your day. Thanks for the advice. 🙄

 

Not to get in the middle of this, but we had a 4G64 block blow a Cometic at around 30 lbs on an hx40.

After pulling it down, head and block were straight, so we threw a modified IX gasket on it, she holds over 100whp more just fine.

I have had a Cometic hold damn near 50psi though as well. Could be hit or miss.

 

Yes it seems it is hit or miss but I always have to assume someone installed it incorrectly try and I gave it a shot and bam... failed.

How did you machine the oem 9 gasket? My thing was sandwich the gasket between a block and torque plate and bore it out. It’s not much... like 1mm total is all it needs when I measured it up

 

That’s what happen to my cometic, cyl 1 & 2 leaked to coolant passage on wastegate on low timing and ballooned radiator.

 

Here is evo9 (top) next to and evo8 (bottom). Both gaskets hold 40-50psi easily but you can see evo9 top gasket pistons touching the gasket and was causing detonation.

 

I had the gasket for a long time, got it in a part out. I think AMS did it, I don't know if they still make them to purchase, but I believe that's what goes in their 2.4 builds.

 

Yeah they dont do them anymore. I tried

to update this, I put the cosworth in and sent it 40psi for a few pulls and tons of wastegate pulls to simulate the type of racing I do (not 1 time glory pulls on the dyno) and it’s holding perfect. Coolant pressure logging 14-16psi the whole time. So that’s both the oem mls and cosworth holding perfectly over the cometic on the same surfaces. The cosworth being the right size opening for bore I’m getting no detonation now over the oem mls. Plugs are clean, burn is clean. Hopefully the next guy that does a 2.4 finds this thread like how I wish existed and makes the right choice to stay away from cometic... unless you want to gamble

 

I was gonna guess your problem being you have beans for rods :P Congrats on finding the fix! Hopefully it holds together for ya.

 

Fwiw, most of my Cometics have failed one way or another. Never had issues with OEM, never tried cosworth though. Does HKS still make 2.4 HGs?