BBC .904 lifter

It's eating the exhaust and taking the cam out. Valves were check before the run that killed it. This is the 4th time a different cyinder each time. As far as valve float it has 350 on the seat. We use a waste spark ignition that fires on the exhaust stroke of the mating cyl I was wondering if this could cause the valve to float. Thanks Craig

 

Valve spring pressure itself is not directly a component of resonant valve train separation. if you could shim your spring to add another 100 pounds of pressure, the resonance and separation will still occur, continuing to beat up the parts at the same rev values as before. Traditional "valve float" can kind of be thought of as a separate subject, usually considered to be when the valve spring cannot control the valve motion at a high RPM, as inertial values (aided by boost pressures) exceed the abilities of the spring pressures. Resonant separation can happen at a number of different and distinct RPMs in your operating range, with the general appearance of valve float having happened. Is there distress on your exhaust retainers/valve keeper grooves/locks as compared to the intakes? Due to different intake and exhaust valve train weights, these resonant points can be different for the intake vs. the exhaust valves. And the rev limiter style can also be a cause. Expensive to experiment with, but eliminating the limiter and changing the stage RPM would be one way to test this. Make a 60' run and inspect everything to see if the staging revs are doing the damage. Obtain the resonant RPM values that your cam grinder should be able to supply, and Spintron testing would be very helpful (also somewhat costly, but you won't blow your engine up). These should help provide some clues. Regards, Chase