81 cylinder head vs 67 head

[67belevdere/225]

I heard the the later head is a better design,
the one on my car I ported it and new valves and all shaved it .100"
I bought a spare engine and it came with a rebuilt head , its casting is from a 81
is there any power or better performance in having the later head.
I would port it and open it up also.
thanks

 

[Garrett Ellison]

I doubt that there’s going to be much difference in the early and the late heads. @RustyRatRod has some pictures of a very ported and really unique prototype head that if nothing else, is amazing to see. He would probably know at least a little more than I do (which ain’t much!) about slant six heads.

 

[doug 371]

hardened seats would be a bonus

 

[RustyRatRod]

Well first off, the slant six received hydraulic lifters in 1981. So, that head is totally different than the 1980 and prior. The valve cover is even different and non interchangeable to the 1980 and prior. That said, there were a couple or so "revisions" of the slant six pre 1981 head. The best thing to do is read this:
Revised SL6 Combustion Chamber