"Do not allow over clearance for the pushrod. This may cause the pushrod to move around or deflect more then needed. Clearance of .010 to .015 on aluminum heads at the closest point of contact is sufficient. We also need .015 to .025 clearance at the lifter bushing or tie bar of lifter. The surface of the cylinder head or engine block can often be utilized like a large guide plate and dampening device which stabilizes the pushrod. Make sure there are no pushrod binding or interference problems when turning the engine over during assembly."