Another comparison shot. On the left is the old-style head and on the right is the new head. As you can see, the chamber in the new head has a slightly sharper curve right around the spark plug hole. Engine builder Charlie Long tested both heads back to back and says that despite the differences, the two heads produce the same power. What is evident, however, is the casting quality of the new head is much better. Engine builders should see less core shift, casting flash, and overall aggravation.