[Superman]

I'd agree that if you lose oil pressure you'll have more problems than just tensioners or bent valves. I'd also add that hydraulic tensioners are actually kind of "hydraulic assist" tensioners. They are very much spring loaded and they keep my chains quiet during the roughloy 1-2 seconds between startup and full oil pressure to the cam oil lines. I can hear them growl during that brief time. I timed my cams with only the spring tension of the PF tensioners because these internal springs held my chains TIGHT. So no, they don't rely entirely on hydraulic pressure.