ive got a 408 9.5:1 alum. heads, alum. radiator, maradyne single fan (switched from black magic)...the block is filled to the bottom of the freeze plugs (before everyone blames the fill, my last motor didnt over heat, it was a 11.25:1 347) im not running a thermostat..

any ideas??

 

I'm a bit of a retard but, "the block is filled to the bottom of the freeze plugs" so, is it full of coolant or not? And, if so running without the thermostat will not allow the coolant to cool off because it is in and out of the radiator before it as a chance to do its job. And, of course there's the ambient heat, my Cobra(5.8L w/11.5:1 compression) is running @ 195 degrees in the hottest part of the day and 180 in the late night/early morning of the day.

 

like said put a thero. back in it. whats the timing set at? do you have the lower air deflector on the front of the car? when does it over heat running down the road or sitting still? look into a high flow water pump. also what rad is in it ? I know you said aluminum but how big is it. you might also need to move up to a bigger fan if it is doing this sitting still

 

More info buddy, I had a major overheating issue a while back ALL related to 302 MARCH underdrive pullies.

 

Lots of reasons for overheating. Start by either putting the thermostat back in, or putting in a restricter plate. Without that, the water flows through the heads so fast they don't have time to absorb the heat. Then when it gets to the radiater, it doesn't have time to shed the heat.

Next, check timing. Use a dial back and make sure the advance is doing what you think it is. You might be surpised.

FInally, check your fuel mixture. Lean mixtures run very hot.