MLS Headgasket measurement VS Bore size and availability
 

Attempting to order head gaskets for my motor after valve bending incident. Bores measure 4.56, and gasket measures 4.58. Talked to a very good wrench and he said to order by the bore size, order 4.56 x .040 Cometics from summit. Did not realize the delivery date is 7/5. WTF? Now the two below are available will ship today. BTW, the gasket measured just a touch over .040. Can I use either of these?

Fel-Pro 1075 - Fel-Pro Performance PermaTorque MLS Head Gaskets, 4.580 in. Bore, .041 in. Compressed Thickness, Chevy, 366-454,

Cometic C5433-040 - Cometic MLS Head Gaskets, 4.570 in. Bore, .040 in. Compressed Thickness, Chevy, Big Block, Each

Thanks,
Jeb

Call Cometic and get your gaskets from them directly...

Anyone else?

I had better luck with the Fel Pro MLS vs the Cometic.

Lay your used 4.58 bore headgasket over your cylinder heads. if they come within .010" of of cyl heads combustion chamber,then the 4.570 won't work for you.

It is better to go a little bigger bore on a head gasket, than it is to have any of the fire ring stick into the combustion chamber, which won't work at all of course.

Even cometic says .010" larger on head gasket bore vs cyl bore or cyl head combustion chamber (which ever is bigger) is no big deal. Some say even a little larger than that is no big deal.

Cometic makes these to order, so they are 5 days out then ship. I believe these are Felpro.

Your typical replacement gasket for a 454, 4.250 bore, is a 4.370 bore Fel pro. A typical 502 replacement gasket, 4.47 bore, is a 4.540 bore gasket. Millions of them running around just fine.

I would have no issues with the felpro 4.580 gasket on a 4.560 bore, providing the gasket matches up to the cylinder head's bore. Like SB said, you definitely do NOT want the fire ring protruding anywhere.

I ended up with 4.58 as I put it on the head studs and was just where it needed to be. Thanks for the input everyone.

i have used the fel pro 1075 on quite a few 4.560 bore engines with good results.i like fel pro better than cometic,just personal preference.

What heads do you have? Like sb said combustion chamber may be designed for a 4.600 bore gasket.