Hey guys im back with still the same issue! As i had said in another post i bought a predator that had dropped the exhaust valves into the piston. I replaced the valves and timing chain and reassembled after struggling with spum camshafts. i finally had time and money to work on the pred and still nothing. I have brand new webcam camshafts installed and i bypassed the fuel pump. As i said before i have new valves. I have done a leak down test and it seems im losing air out the exhaust when piston is at the bottom but it seals up when i start to turn the motor over. When at top dead center and i apply pressure it has no leaks at all when testing at 15psi. However i did a compression test and came up with barely 35psi! What could be causing this suddenly? Timing off? It cant be the piston rings can it? There was no air passing the piston rings going into the case or i would have heard it and smoke would have revealed the leak. I have fuel and spark so im clueless! I really need some help.

 

You did not mention anything about replacing the piston. Was it not damaged? If it has low compression, obviously, it must be leaking. The head may be cracked, could be a bad head (warped) or base gasket, the valves may not be seating, cracked piston or cylinder, bad rings. I know this isn't much help, but you have already determined the problem, now you have to isolate it.