When checking for bent valve on an import motor one time I aired up the cylinders and on the good straight valve ones I could smack the top of the valve pretty hard with my 2-3lb sledge and it just shot the valve right back up so don't worry about putting a little downforce on it when doing the seals. Aslo be careful when airing up the cylinders as it will push that piston to BDC pretty fast so don't have your hands wrapped up in the belts when turning the air on. And I just let my compressor run and stay on max psi which is like 125-130 on mine.
