I got a quick question about 84mm vs. 83mm head gasket.

Recently purchased a Cometic HG from Good-Win, by mistake the one I received is 84mm, instead of 83mm, which the BP engine block is not bored.

Just to check how different they are I had a spare old 83mm factory metal head gasket and placed it in top of the new Cometic 84mm. Spent like 5 minutes comparing the two and could not see a difference.

I want to prevent to go through the hassle of returning it, wait for the other one, the car has been in the garage for a while and want to put everything back together.

Is it possible to use the 84mm Cometic on the 83mm BP block?

It "seems" to the naked eye that both gaskets are the same bore size, besides that the quality and craftmanship of Cometic is evident.

 

I'd play it safe and get the one that's right.

 

get a micrometer, open 1mm, try to see through it, notice that it is virtually nothing and then proceed to install the HG into your car.


now, if you were bored to 84mm and had an 83... that would be more of a problem.

 

Don't thicker headgaskets raise cylinder compression?

 

No, a thicker gasket will lower compression