What you can do is a cylinder leakage test. You'll have to set the belt back to correct and get an air-hose to spark plug like adaptor. Some high end comperssion testers have it in the kit. I made mine, Hollowed out an old spark plug and welded an air fitting to it. The goal is so you can plug your air hose to a cylinder that's on TDC and it should equilize and be pretty much silent. If it's hissin from the Dipstick = Piston Rings, Hissin from the tail pipe = Leaky Exhaust Valve Seat... Hissin from the Throttlebody = leaky Intake Valve Seat or in this particular case with sliped teeth on an interfearance motor may be bent or damaged valves with good seats haha...