Head Gasket Choice for 1970 LT-1

[Larry E.]

Hello:

Will be putting original heads back onto the 1970 LT-1. I was thinking of
using part#10185054 gasket from the GM Performance Book. Is this a good choice
for this engine? Gasket is composition typed with pre-flattened wire O-rings.
Note in book indicates no re-torquing is needed. Does anybody know if this
gasket goes on bare or if it needs some type of sealer? If so what kind?
Any advice would be appreciated.

Thanks; Larry

[Duke W.]

Re: Head Gasket Choice for 1970 LT-1

You should choose the gasket to obtain the desired compression ratio range which is 10.25 to 10.5:1 for engines with the LT-1 cam. This ratio will accept premium unleaded fuel without detonation.

It should be easily achieveable with OE machined components, but you need deck clearance, head chamber volume, piston volume, and then run it through the following compression ratio calculator to find a gasket thickness that yields the desired CR range.

http://www.csgnetwork.com/compcalc.html

The following is a partial list of the score or more of available SB head gaskets in order of compressed thickness from .015" to .045". Shim gaskets will seal if the head and block deck measure flat with a .0015" feeler gage and machinists bar, and they don't require retorque. Composition gaskets will typically seal with up to .003" warp, but some recommend retorque, which is a PIA on a SB.

Brand Part number Type Bore dia. Comp. thickness Notes

Felpro 1094 Shim, coated 4.100" .015" polymer coating
Victor Reinz 1178SSB Shim, st. steel 4.100" .020" stainless steel
ROL 31600 Shim, coated 4.090" .024" polymer coating
GM 3830711 Shim, painted 4.080" .026" possibly discontinued
Victor Reinz 5746 Composition 4.100" .026"
Felpro 1043 Composition 4.080" .039"
ROL HG31000HT Composition 4.125" .045"

I don't know what specific part number gasket is in the kit you refer to, so I can offer no specifics.

Duke