Can 516 heads have the exhaust valve and port bored out to the same size as a 915? The bigger exhaust valve would be a huge improvement, and with the closed chamber I could achieve a good quench.. I have some 915's that were decked too much, with my setup. I got kb flattops and I'd end up with 10.2:1. Too much for a street build, I'm running a xe275hl cam, I was shooting for 9.25-9.5. So since I already had the block decked to zero I thought if I can find some untouched 516's and get a 1.74 exhaust valve in there it would be the same but I'd get my 9.5. ??