I have 2 Chevy small block V8's that start and run good when cold and/or warm but when it gets to normal temperature and it's turned off, it doesn't want to turn over. It sounds like it has too much compression. Once it cools for 10 minutes, it starts right up. I've checked timing to be right and have changed grades of gas. Any ideas? One engine is a '76 350ci, with a 600 CFM Carter, a Comp 270 cam and Corvette alumium heads. Auto trans. The other is a '68 327ci manual trans with a 600 CFM Holley, a Comp 268 extreme cam and double hump (non fuelie) heads.