Ok so putting this in a new thread simply to get fresh ideas. I have a 98 grand prix se 3.1 L. Replaced head, manifold gaskets and a few other worn parts. Go to start and it wont start. Cranks but wont start. Double check and still no start. It did start on 2 different occasions. Turn it off and wont start again. So I check the timing chain.. take it off and re adjust the timing put everything back and wont start. Turn the crank pully by hand and it only goes a little then stops. Same in the other direction. All plugs are out ! So its not comppresion. I tuned the valves after replacing the head gaskets. But if the timing was off and now has been reset, could the valves be causing it not to turn? And need to be retuned?