It looks like the 98-99 Heads have round exhaust ports and the 2000+ have oval ports. What is the reasoning behind this? There was no listend performance gain from 99-2000.

Also will 98-99 headers work on the 2000 heads sans emmisions?

 

I have 98 heads that i am porting and they have oval exhaust ports, stock. One difference i know of is later 2000+ heads have better flowing intake valve than 99 and back. Difference is from 5.7 to other heads like 5.3, etc they seem to have different exhaust ports than 5.7.

 

Then why the two sets of gaskets in the head swap kit?

 

Corvette LS6 has different exhaust port shape and takes a different gasket, until 2002, now new gasket works on both styles.