When ordering head gaskets how should the bore size of the head gasket relate to the actual bore size of the motor? Like I have a 360 that's .030 over so its 4.03. Cometic makes a 4.04, 4.08, 4.125 and 4.18 gasket. Would the 4.04 be okay to use, or should I use the 4.08?

I would probably choose the 4.125 or maybe 4.080 so the inside edges don't squeeze into the combustion chambers

Will be using Edelbrock Performer RPM Heads. Seem they recommend the 4.18 gasket (As that's what Edelbrock headgasket is). I see Cometic sells basically 2 gaskets per compressed thickness. One has a note to be used with Edelbrcok Heads, so maybe its made differently for the Edelbrock heads?

If Cometic has a 4.080" of the type they recommend for Eddy heads then that is what I would choose.

may be 4.030 bore but how big is the chamfer at the top of the bore,you don't want the gasket to extend into the bore, some have way too big of a chamfer.

^^^ agreed, forgot about that.

Question. How does the inner diameter of a steel circle get reduced by clamping load?

I called Cometic today and the tech guy recommended the 4.080 gasket. Just curious if anyone with the Edelbrock heads have used this size?

Edelbrock makes a bunch of different aluminum heads for the 318,340 and 360 motors, most are 65 CC but one or two are 63 CC chambers