Originally Posted by 2manyhobyz
I also cc the head tonight and found that stock combustion chamber is 50cc. The Supertech head is more like 49.5.
??? You mean a head with Supertech valves? I could see that as the larger valves would take up just a tad bit of volume because of the larger diameter. If you had the valves sunk, the volume would go up.
As far as the valve angle goes. The 99 and newer head has the same valve angle as the older head. The only real difference in the design is the fact that the intake runner has been raised significantly.
Most piston manufacturers make the valve pocket wide enough to clear oversized valves and deep enough to clear larger lift cams. However, it is up to you to check your clearances to be sure that they are sufficient. You will most likely not have problems with the common popular pistons.
I had a problem with a set of JE high compression pistons that I had purchased quite a few years ago that did not clear my oversized valves, when I changed to a modified 99 head. It was very close, and I was able to clear the pockets with aggressive grit sand paper and a little time.
I was very suprised that JE would not have made pockets wide enough to fit larger valves, but I guess at the time most racers were not using larger valves when the pistons were made.
So yes, clearance problems could happen, and if you are running anything exotic, your chances of problems go up. Those problems can be corrected however. Just be sure you check everything.