X-heads vs J-heads: what's the difference??

A bigger valve is not going to be better sometimes. Remember, the bigger the intake valve the more it get shrouded. aka restriction. yes you can help that with a die grainder, BUT only up to the head gasket seating area, Then You Are Done!


Some one else said that a bigger valve will give more flow at lower lift. This is true. but if you have reversion problem(exhaust gas being push back up the intake during overlap). A bigger valve will magnify this problem. or start, a problem that you didn't have before!