I have a 350 with flat top pistons and I will be putting on Edelbrock Etec 170 heads this weekend. I would like the compression to be 11:1 and the only way i can get it there is to use a steel shim head gasket .018-.020 thickness. How well would these seal aluminum heads to my block? Should I just go with GM's composite ones (.029 thick)?

 

Well the instructions don't say anything about putting shim gaskets on but they do recomend the GM .028 ones, I guess I will go with those.

 

Should I just go with GM's composite ones (.029 thick)?


Yes... I believe the part # is 10105117

Do not use shim gasket on alum.

 

Look into Felpro 1094 gaskets for the alum. heads.

 

if you go to a thinner head gasket you will be loosing piston to head clearance. it really needs to be .035 or more for safty. also going down even .020" will only remove 4cc's.it might get you to 11-1 if all other dementions are really tight. so you will end up with an engine that will probably need 94 octane minimum and the pistons may hit the heads. if however your deck hieght has the pistons .025" down the bore, which is standard on 350 chevy you won't have a clearance problem, you won't get near 11-1 compression, and the steel shim gasket will ruin your aluminum heads. there are however coated gaskets in the .025" range available for this purpose that may help.