Checking piston-to-valve clearance is a crucial step. Aggressive camshafts open the valves a greater distance and for a longer time. As such, there is a greater risk of experiencing piston-to-valve interference. The clearance in this engine was well over .100 inch thanks to the valve reliefs in the Ross pistons. Piston-to-valve interference is obviously a very serious problem that will result in bent pushrods, bent valves, broken rockers and even broken pistons.