Fuel??timing ??or both??

did you test the thermostat before you put it in? i have gotten 2 bad thermostats in ONE day. take the thermostat out and see what it does. a cold upper and hot bottom radiator hose after running for 10-15 minutes is for sure a thermostat that isnt working. ive ran 318s and 360s with slant 6 six radiators that worked fine. check them in a pot of boiling water to make sure they are actually opening.