Hey neighbor!!!! Well the 781's are NOT closed chamber, they are open chamber. As a matter of fact no GM oval port heads are closed chamber. They are mid 70's 454 truck/car heads. They are good heads and out flow rectangle ports at low-mid RPM's. They also respond very favorably to some bowl work. You can easily make 5-6 hundred horsepower with those heads set-up properly. I have a few books that show exactly what needs to be done to them that I will dig out if you like. Good luck!
[ August 25, 2002, 10:30 PM: Message edited by: skeepwerkzaz ]