I don't have any answers for you but I'm hoping it isn't much.


I'm basically going from a 363 to a 408 with the same heads but a bigger valve, 20 cfm more flow, a solid roller from a flat tappet but the duration at .050 numbers are within 1 degree of each other but about .030 more lift. Since I can only buy 1 ratio of pro gear for my 8.75 it's much harder for me to change the RPM range I can run the car in. However since most racing down here these days is 1/8 mile it's a lot more forgiving.