It may well be that your springs aren't strong enough. If they are stock they may not have enough tention to hold the valves closed under load. It might be worth your effort to contact the cam manufacturer to see what specs they recommend on the springs. Your shop guy should be able to measure your spring tention and see if it's close. If you have good oil pressure(lifters bleeding down) and your not popping back through the carb or the exhaust under load(timing)your only left with the valve springs. This would account for the valve float and maybe even your being able to bottom out the rockers. If the springs aren't strong enough the valves may be opening when you bottom out the rockers and not the lifters. I can only think of one other cause and it would affect the whole RPM range, the rocker studs may have backed out. I don't believe this is the problem though. Still scratchin' :confused:
