I have a 79 former 351M with Tim Meyers help is now a 408. Here is the problem: We are trying to break in the engine but after 2 min. it is up to 180 degrees and the radiator is cold so we shut it down. It has a March serpentine system that came with a new water pump. New thermostat and Eldelbrock intake. What are some possibilities as to the problem?

 

What thermostat do you have in it? 180F is not too hot for a engine. Some thermostats don't even open until 195f. I wouldn't be concerned about engine damage until well over 200.

 

I agree. The bypass system on the 335 Series engines is below the thermostat, so flow of warm coolant won't heat the 'stat very much. And the correct 'stat is a 195 degree unit, so it won't open at all until you get close to that. Until then, all the flow is in the block.

The only way there isn't flow is if the water pump's vane isn't spinning. If you are sure the vane was attached to the shaft and you can see the shaft spinning then there is circulation. But you can put another temp sensor in the water jacket to ensure that's the case. IIRC there's a plug in the block in the left rear that can be used - although I can verify that later today if you want as I have two blocks on engine stands.

 

I would not want to run any engine less than 185 degrees. You can get sludge build-up if your oil never gets up to temperature, at least with conventional oil. I agree with j ballan - and wouldn't worry until you're over 200.

Good luck!