I changed the timing chain, guides, tensioner, oil pump seal on my 88 22R truck. When I put it back together and tried to turn the engine over with a breaker bar it turns 1/2 - 3/4 of a turn and stops, however the engine starter spins it over and over. It also makes a sqeeking noise that sounds like it's coming from the oil pan (not a metal on metal noise). Any ideas why the engine stops like a valve is hitting? I checked the valves and they are not hitting the pistons.

Thanks for the help guys.