[Stock96]

I have a 96 GT and recently rebuilt the top half of the motor. It ran great and this morning I went to start it but all I heard was a horrible sound and now it won't run worth a damn. My fear is that a tensioner lost pressure and allowed the cam timing on that side to slip. When rebuilding i noticed the right one had problems priming and it took quite a few revolutions to get it up and snug. The car sounds like a lawn mower when it will fire and won't run but maybe a few seconds. It literally sounds like a 2 stroke lawn mower.

My real question is how does one diagnose broken valves without tearing off the heads. Retiming it and replacing a tensioner is not a huge deal to me, but it'd be pointless if I broke a valve during the process. Compression test won't work if valve timing is off, and I'm not balling enough for a bore scope. Any other ideas?