Realfast86

Whats the best head gaskets to use on a LSX block with 4.125" bore Cometics,Felpro,GMPP? and what bore size?

Realfast86

Crickets!!!!!!

lane_change

I went with a Cometic 4.205 bore .045 thick head gasket for my 4.165 bore RHS block. Most of the time I prefer to stick with GMPP when possible, but I couldn't find one for my bore size. I know Cometic had some issues in the past, but I've been told that they are working well now, so I'm optimistic.

Unreal

I'm running the GMPP ones.

Realfast86

GM next size is 4.200 and Cometic is 4.185" is that to big for a 4.125" bore i thought the basic rule was around .030 bigger and what would the larger gaskets due to the comp.?

EX1

Never had an issue with GMPP or Cometic

Tuomas FIN

Plus 1

Realfast86

So what size gaskets are you guys running and what is your bore sizes?

realcanuk

Bore 4.005

LS9 gaskets. 4.10

Unreal

4.125 and 4.2 I believe. Whatever is the next size up from 4.125 in the GMPP gasket.

ProEFI

Cometic FTW

lt1z

GM 4.200 Gaskets

19170419

Realfast86

Talked with Cometic today they said they will make any size gasket i want same cost as shelf gaskets just takes a few days so the question is what size should i get 4.155" and also i was planning on .051 thick should i do .040 that would take my comp. up to around 9.6* VS 9.4* will that matter much with twins?

Unreal

Either one is low. I would go for 10:1.

Realfast86

It will be mostly on pump 93 no corn around me!

Unreal

Would still up it. Best setup I've seen recently was a 416 10.5:1 twin 56mm car. Made 920rwhp/940tq on 10psi pump gas and turbos spooled at ~2k and had a sick power band.

Chance42

If that's the 5th gen I think you're talking about he had meth injection as well. I think he is also about to rebuild the motor again unfortunately.

Unreal

Nope and nope.

Realfast86

I got the details from the builder today and used the chart to figure out the Comp ratio 4.155 gaskets 0.040 are 9.85-1 and .051's are 9.64-1 builder said no worries on PTV clearance with the cam i'm using!