Chrysler called the chamber the OP has a closed chamber. What the OP gained in power form the CR he lost (and then some) in airflow.
That's about the worst thing you can do to that chamber. I've been telling guys for years to stick the piston out of the bore like Chrysler said, rather than do that. It just doesn't work very well. Even with a 50* seat. Believe it or not, it really likes a 55* seat and a big tulip on the back of the valve.
