LA Head Gasket?

[512Stroker]

I have a .030 over 340 LA engine dated 1969, street application
So the bore is 4.070
I am looking to up the compression ratio from it's current 9.5:1 static
Current head gaskets are Mahle 3536SG compressed thickness - .045
I dont believe the sealing surfaces will hold a steel shim head gasket.
Does anyone have experience with a thin composite head gasket around .025-.030
Manufacture?

 

[70aarcuda]

Mr gasket 1121G

 

[brian6pac]

Cometic makes a .020 or .025, can't remember.

 

[oldkimmer]

That little bit isn’t worth the hassle. Kim

 

[rumblefish360]

Cometic makes a .020 or .025, can't remember.

I ordered and run a .028 from Cometic

 

[RustyRatRod]

It's my understanding Cometic will make pretty much whatever you want.

 

[Dartfreak75]

I like felpro 8553

 

[B3422w5]

I used the 028 mr Gasket. It seems very forgiving. Several of guys I race with had good luck with them.
Surfaces were not a big deal, no leaks

 

[512Stroker]

That little bit isn’t worth the hassle. Kim

Good point Kim
How much static compression would be gained in a 340 by going from a .o45 compressed gasket to a .027 ?

 

[oldkimmer]

Probably .2 if ur very lucky. U could always have the heads milled .030. Kim

 

[512Stroker]

It's my understanding Cometic will make pretty much whatever you want.

I would prefer Cometic gaskets but I dont know if my sealing surfaces a good enough. They heads have the stock factory surface and the block was squared and decked 3 years ago/6500 miles.

 

[brian6pac]

Spray it with copper coat, you wont have any problems.

 

[Scody21]

Spray it with copper coat, you wont have any problems.

And a thin bead of RTV around the water port holes in between the gasket layers.

 

[brian6pac]

And a thin bead of RTV around the water port holes in between the gasket layers.

The thin gaskets are a single layer but if you have a multi layer, I have done that.

 

[RustyRatRod]

I would prefer Cometic gaskets but I dont know if my sealing surfaces a good enough. They heads have the stock factory surface and the block was squared and decked 3 years ago/6500 miles.

Tell them you have crappy sealing surfaces. You need a crappy sealing surface head gasket. They'll hook you up.

 

[AJ/FormS]

at 4.18 gasket bore
.045s are about 10.12cc
.028s are about 6.297cc
the difference is 3.82
on a 10/1 340engine at 4.07 bore, the swept is 706.754, so the total chamber size would need to be 78.53cc...
dropping that to 78.53 less 3.82=74.71 total chamber volume ,
and that would get you 10.46Scr

edited for fat-finger typing; I think I got it right this time.