I agree with every thing so far, but on the timing deal how does it start after heat soak? If it starts right away then u have a cooling prob like air flow getting around the rad instead of thru it. Or with no thermo. the water is not slow enough. Motrcycle guys sometimes get their bikes cooler by dialing in more fuel whivh helps to quench some of the flame. And sometimes with fords u cant set the timing totally with a light. Hope this helps I have a many a big block rodeo, but I still go back for more. RDHOTFRD