NHRA specs were 123 cc's. Like Joe said, they do vary. If you do any chamber work that of course increases. The stock tulip intake valve's tulip is 2.3 cc's. So just by going with a flat faced valve will decrease volume. Tom T.
The NHRA provides the minimum allowable specs: not average. Just like 1970 stock 455 heads do not average 59 CCs, but that is what the NHRA specs. Cheryl
