I had a problem with broken manifold bolts in my 862 heads so I found some 706 heads to run that we’re all ready to go. I put a new head gasket on as well and got the whole engine together. Went through a got oil into the heads and when I went to crack it over to start it rev up than stall. Sometimes I says to check oil pressure. I’m not sure if the timing is off or if something happened to my oil pressure sensor while the engine was apart.