New Motor wants to run HOT

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jefflock

jefflock

69 Dart 408 10.08 best pass so far
FABO Gold Member
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I rebuilt my 340 and now it wants to run hot. Everything is new including a second thermostat. It warms up nicely but wants to contiue to get hot. It seems the longer it runs the hotter it gets. I had a 7 blade fan with no shroud, removed it and fabricated a shroud and mounted an electric fan on it. No change. With the 7 blade fan I could rev it up and cool it somewhat. Since the temps here in Kansas have climbed to 95+ I've just been not driving it. The radiator is a 3 core model. Any kind of mechanical issues I might might have missed? I've checked and reset the timing. Is there such a thing as putting the head gaskets on backwards blocking some cooling passages? The motor is warmed over with a Holley 750,Lunati cam, stock pistons,alum intake and headers. Thanks Jeff
 
You may be running way to lean. Check for a vacuum leak or wrong jet size. Did you have this carb and intake on this engine before? Not sure on the head gasket, been way to long. Hopes this helps

Paul
 
How hot is hot? Being the motor is new and tight it will generate more heat from the friction but will lessen after getting some miles on the car.

Chuck
 
make sure that you have the rubber seal that attaches to the underside of the hood that seals to the top of the core support.
 
Did you change the water pump? If so, did you wind up with a reverse rotation Magnum pump by mistake? Did you use the 340 to replace a 318? I bring that up because the first 340 I had caused some anxious moments; the temp gauge was suddenly in the middle of the range and I was used to seeing it at the lower edge of normal with 318's. Hope this helps.
 
I would run the mechanical fan with the shroud. Have you driven it yet ? Does the temp drop when its moving ?

Could be lean,Timing to far retarded, air flow threw the radiator.
 
It does drop while driving but when you cruise around it comes up. At 220 I shut it off to cool. I'll check the jet size. It should be what ever the 750 vac sec Holley came with. And I'll advance the timing to see if that helps. Thanks Jeff
 
you can take it to the radiator shop have them check for a blockage in the radiator.this happened to me. they found the problem after i changed the therstat,water pump.put a shroud on and flushed the motor and radiator and still had a problem ! they roded the thing out and now the whole system is brand new !
 
what kind of thermostat and water pump? if it is a higher flow water pump, you should use the milodon or mr. gasket brass thermostats. they open with the flow of water. stants open against the flow of water and can be pushed shut.
 
what is your source of info telling you are overheating? if its just the gauge..it is actuate? double check with a heat gun. Water pump working? use a flow gauge installed in the heater hoses.....could be as simple as air in the system.Make sure you bleed it proper. Use a heat gun to pin point hot spots in the heating system.
 
The water pump is new from NAPA and is the correct type, the radiator is a new 3 core,the thermostat is new from motor rad (fail safe type). I put the 7 blade fan back. (No Shroud) Added water wetter, bumped the timing up to 15 degrees intial 34 total. Seems to be working better. I believe it's an air flow problem. I'll try to build a shroud for it. Jeff
 
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