What heads?

[graycamaro]

malihoochie are we talking pro stock drag cars. Because most drag cars especially higher classes such as top fuel care very little about valve jobs. If you saw how crude those engines are put together you would be in aww. generally speaking all they do is put a seat in grind a 45 degree seat and stick a valve in it. Seeing as these cars only run for a couple of seconds at a time it doesn't matter if the valve job last or not. whereas on a street car, stock car or road race car this becomes very important.

On most Dart heads I have seen brand new untouched the exhaust seat is very wide for a performance application and the radius cut they put on the top of there seats does alot to improve flow on a bench but if you look at how far that puts the valve down inside the chamber it is going to take more valve lift to get the valve out from the hole its in so it can breathe. Also a radiused bottom angle on the exhaust causes the seat to wear very quickly.

I work at a machine shop here in Il and we do everything from turning drums, rotors, flywheels, to machineing blocks, heads, rods, grinding cranks, and we build everything from stock engines to restoration engines, high performance street engines, and racing engines. Most of are racing engines are for dirt track stock cars and road race cars like the a AS cars that run SCCA. We have also done swamp buggie engines, tractor pull, and some drag car engines. So this is where my experience comes from.
I am speaking from things I have personally seen as well as what my boss has shown and explained from his 30+ yrs of experience.

James