I'm getting ready to purchase Cometic head gaskets for my F/I build. The block is a 1-piece seal SBC (non-lt1) with a 4.030 bore. I've always ran the Fel-Pro 1003 gasket (both N/A and Boosted). This has a bore dia. of 4.166. Cometic offers their gaskets in 4.060, 4.100, 4.125, 4.165 dia.'s. Each of these are different cc's, affecting the final compression ratio (even though its not much between them.) Is there any advantage or disadvantage to running any certain dia. gasket? What woud you guys run?

Thanks

 

I'd call the manufacturer...they would know better than anyone. And, they aren't cheap, so it would suck to spend the money on the wrong ones!

 

The gasket should be at least .010" larger in diameter to accommodate differences in thermal expansion rates.

An excessively large gasket bore will give you 'less gasket' between cylinders and cylinders to water jacket holes, so probably not a great idea.

For a 4.030" bore I would just run the 4.060 gasket. The final compression ratio difference from a slightly larger gasket bore is only like a few hundredths of a point. They can be ordered in any thickness by the way.

You'll notice most suppliers are 2 weeks out on cometic gaskets, this is because they are all built to order and not usually stocked.

BTW I got mine from byunspeed.com for $75/each and free S/H, they were $90/each everywhere else
+ S/H.

 

Just an FYI, I called Cometic and they recommended that i use the 4.060 bore gasket with a 4.030 bore. Jegs has these in stock to ship today also! Thanks for the replies.