i have a 383 eng hi po street eng with 4.280 bore what bore head gasket should i get, looking at cometic head gasket but do not see a 4.280 bore size gasket,what thickness should i get to add a little more compression,has a solid lifter cam,headers,holley 750,has 915 heads that has some work done to them.60 over flat pistons.thanks

I just measured my 8519PT1 felpro blue BB head gaskets & the bore is a strong 4&1/2". they might compress to .051" same as the comparible 8553PT SB similar blue ones that compressed to .051". how far are you in the hole & what is your SCR?

On your build IF your going to run pump fuel make sure and don't get the compression ratio over 9.75 to 1
How far down in the bore are the pistons now? Do you know how big in CC your combustion chambers are? If not find out on the deck heights and the head CC before buying your head gaskets

Cometic has a ton of sizes and thicknesses. 440Source or Summit. Just get the 4.350 bore in the thickness you want. All the source gaskets are 4.380.

383s came stock with steel shim head gaskets, the thinnest gasket one can find. The compressed thickness of the composition gaskets is usually in the 0.040" - 0.051" The steel shims were something like 0.018" when compressed.

You want to have a gasket big enough that it does not hang into the bore, chamfer or combustion chamber. Thus, 4.28" head gaskets would not work well on a 4.28" bore.

Compression is hard to find on a 383, unless you spring for a set of custom pistons. How far down in the hole is the piston at TDC>

R.

To make a good choice, you need this information...........