Originally posted by holycowSVTpaul:
1. Also, the NASCAR heads tend to be extreme improved versions of the old 60's style head chambers. Flow/distirbution is addressed with runner, manifold, mirrored port and head angle design.
2. Well, open chamber heads on a smog era SBC had better air flow characteristics than the 60's. However, the 1960's era heads made more power and it wasn't just because of higher compression. It was due to the better burn characteristics of the heads or better quench.



1. ...and comparing oversized 2-valve extreme lift race heads to a 4 valve hemispherical shaped head run via roller followers and dual low lift camshafts is a great comparison...

2. Unshrouding the valves is a good thing. It promotes better air flow and chamber swirl. You are not changing the overall shape of the chamber.

Also then try and explain the fast burn heads and their unshrouded valves. They make better power right out of the box then most professionally ported heads do.

Another thing to remember is that when going 3L you also want to install the larger valves. You'll be changing the area around the valves anyway (not too mention porting the intake passage before them) so not finishing to unshroud them at the same time would be foolish. It does not take a significant amount a material removing to do such.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.