Correct valvetrain geometry is critical to ensure trouble-free operation of an engine, especially during high-rpm operation. When building a new engine, many people simply reuse the original pushrods ...
You're on a par-3 tee and the shot you're facing is either a hard 7-iron or soft 6-iron. You're between clubs, so to speak. The 7-iron might get you there and the 6-iron might put you above the hole ...