Thread: new 350 overheating

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i just built a 350 for my pickup. installed it and timed it. it overheats.
pressurizes cooling system and overheats quickly. removed thermostat and it runs great, a little cool but runs great. installed new thermostat and overheats. am i missing something? i read somewhere that i could have put a latter model water pump and that could cause a problem with the reverse rotation. this is a bare non emesions motor. what is my deal.thanks cody

Replace the radiator.

I have run into this in the past. The newly built motor simply makes more heat. The radiator was sufficient to cool the motor before it was built, but now it simply can't hang. Either have it serviced or replaced.

Cody, you are saying that the motor runs cool with no thermostat but overheats when you install a thermostat. My best guess is that you're installing the thermostat backwards. The pill and spring go toward the motor.

this thermo is installed with the spring down. as for a new radiator? thats just odd. i can imagine that that would be the problem. like i said it runs cool with no thermostat.
thanks cody

Originally Posted by cody1bud

this thermo is installed with the spring down. as for a new radiator? thats just odd. i can imagine that that would be the problem. like i said it runs cool with no thermostat.
thanks cody

Take the thermostat into the kitchen an place it in a pan of water. Put a cooking thermometer in there with it and turn up the heat. Make note of the temperature where the thermostat opens. You may have run up on a dud.

sorry, I misread the post. Thought you said it ran hot with and without the Tstat.

sounds like a bad t-stat...

Hi cody,
bad thermostat or wrong rotation water pump. You should be able to detect a wrong water pump with the casting #. The main problem is if the waterpump turns the wrong way the coolant will flow through the engine in the wrong direction, that's what might be causing the overheating. It should flow from the cooler parts of the engine (block) to the hot parts (heads). That way the heads get coolish water. If coolant flow is reversed it flows through the heads first and then goes into the block hot. That heats the block much more than usual and causes a whole pile of problems, like too hot oil and stuff. So if the thermostat proves OK, check the rotation!
BTW: slight overhating isn't much of an issue for a new engine, because friction is much higher. If it's running just a little on the hot side (with correct rotation and thermostat OK) just pop in a slightly cooler thermostat for the break-in period.
Hope I could help,
Max

well.. i replaced the thermostat
and still running hot. rather quickly.
how would i know if it was a reverse rotation water pump?

Casting # will tell you which rotation it has. Get the casting # and google it. Or you remove the pump, take the back cover off and look at the direction the vanes go. As the housings are the same and only the impeller design is different you wont be able tell from the outside, only with the casting #. On some aftermarket pumps there is a little arrow cast into the pump casing to show the direction of rotation. I think not on stock pumps.

Just read your first post again: If it pressurizes quickly and the T-stat is OK, then it's quite a sure sign of the wrong rotation if all other things are OK. Pressure at first should go into the block, but with a closed T-stat it should stay in the engine and not get into the rad yet. Only when the T-stat opens it should pressurize the whole cooling system. Where exactly do you measure temp and pressure?

And did you measure the ring gaps before installing? No waterpump can cool butting rings... (But on the other hand, butting rings would have killed your engine by now probably...)

Oil pump and oil pressure checked?
Non-standard friction will overheat your engine quite quickly.