Head gasket bore vs compression
 

How important is the bore size of the cylinder vs the bore size of the gasket? Say you have a 4.200 bore and a 4.400 gasket what would be the difference in compression if I went to a 4.250 gasket?

Re: Head gasket bore vs compression
 

There are a lot of variables in CR. Try putting the info you are playing with into a calculator like the one in the link below to see the differences.

http://www.csgnetwork.com/compcalc.html

Dale

Re: Head gasket bore vs compression
 

Gasket bore size doesn't change compression as much as you think, thickness does.

Re: Head gasket bore vs compression
 

Considering an 0.040 gasket, the 4.4 would create a cylinder with a volume of 9.963cc while the 4.250 bore would give a cylinder of 9.291cc.

That's a 0.672cc difference. I don't think it matters a gnats eyelash.

Dale

Re: Head gasket bore vs compression
 

Would a 3.5cc decrease by using a thinner/smaller bore gasket make much difference? .012" thinner, about .030 smaller bore if i remember correctly. Worth changing?

Re: Head gasket bore vs compression
 

Very generally speaking..Yes , you should see a difference.
Worth changing?
That depends on whether you consider this work...or fun.

Re: Head gasket bore vs compression
 

It's certainly a lot of both....but sometimes i wonder . Thanks

Re: Head gasket bore vs compression
 

Chris,
You have to be careful with this. Depending on how much chamfer your machinist put on the tops of the bores you could start hanging the gasket into the chamfer area. I put very little chamfer on performance builds but some guys might put more. All it takes is 030" all the way around and you will be into the fire ring on a 4.250 gasket and that's assuming that all of the bore centers, dowel pin holes etc. are perfectly aligned with the gasket.

4.250 should be safe but its just something else you need to look at.

Re: Head gasket bore vs compression
 

I agree with Dale........Tiny change in compression for bore size variation.