I have a '91 TBI 350 that is showing no compression in the #6 cylinder. I took the valve cover off and every thing seemed to be moving like it should. Are there any other causes of lost compression other than a burned valve or bad piston ring? I'm assuming that the piston rings and head gasket are good cause I think they would show atleast a little compression. Before I pull the head off to check it out, is there anything else that I could try to check or that could cause this? Thanks.