[Keithc8]

One thing that will help you on spring pressure is that the AFR head has a 8MM valve stem valve and they are lighter than a 11/32 valve. Your engine should be fine with 140-150 seat and 375-380@.600 in most cases. What the duration does not tell is how radical the lobe is. There can be 10 lobes with the same duration at .050. I have had 242 lobes that would turn 7000 rpms with these spring pressure and lobes with the same duration float at 5600 rpms. This where knowing your engine, valve train weight and who you are dealing with on the camshaft comes in handy.
Comp Cams somehow ground some LS1 lobes on one of my FE camshafts and the engine would not turn over 5000 before valve float. Could not figure this out because the numbers on the camshaft were stamped right but ground wrong. I knew what was going on and everything else was the same as in the past so sent the camshaft in to have them check it in the cam doctor and sure enough wrong lobes. A bunch of hasle for sure.

Good luck, Keith