It all depends on the combustion chamber design. As a general rule, unshrouding valves will improve flow figures, but then you have to compensate for the increase in combustion chamber size in some way, IE different piston design or cutting the heads.
Unless you have a lot of experience working with modifying heads, I wouldnt try doing it myself.
Pause to think, the guys making the aftermarket heads often have what could qualify for severely shrouded valves, yet they out flow stock heads, to great extent. Could be they are on to something.
While I have always done my own porting, I rely on someone with the proper equipment to do the valves etc. One thing that has been shown to work on most stock heads, despite of the design is to have a 15 degree back cut on the chamber side of the valve seat. This has been known to pick up some serious flow numbers without any real effects on increasing the size of the combustion chamber. As I said, its been shown to work well on most heads. If you are working with an open chamber head like a 2 bbl cleveland, the effect isnt worth the effort.
Last edited by Max Keith; 11-17-2004 at 01:01 PM.