I have a 1973 Plymouth duster with a rebulit 198. New cu in size 210. I am also supporting a set of dultra headers and a 340 duster exhaust system. I am also suporting a "orange" electronic control unit and a 8.25 rear end with 321 gear ratio. I noticed that the first car show I attended, the engine over heated nearly to the boiling point. Just setting and running there is now overheating but when I get it out on the highway, the temperature shoots up. Any Idea what could be the issue hear?

Thanks Bill

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Billaura1972

Crud in radiator, Lower coolant level and look into the radiator you should not see the cores partially blocked.

Richard

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Part of Tyrde-Browne Racing

NEW 2 CORE RADIATOR. ALSO, FAILED TO MENTION, ADDED POWER STEERING AMD POWER BRAKES FOR THE WIFE AND USING SYNTHETIC MOTOR OIL.

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Billaura1972

is your water pump working correctly/ thermostat?-- if these 2 items are ok-- then your block passages are plugged & your radiator is now plugged.

Also make sure you are using a known working temp gauge to verify your engine heat. Lawrence

There are a great many causes of overheating, but in my experience it's most often been caused by (sometimes quite small) leaks (including the radiator cap) causing a loss of pressure. I now always pressure test a system whenever I've opened it up, so you might begin there. Good luck.

Thermostat might be stuck closed if it's heating up on the highway, or not functioning at all.

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70 Plymouth Valiant 4dr

Don't get sidetracked; loss of system pressure is far down the list of overheating causes. Focus on finding and fixing the major issue, which is almost certainly insufficient water flow and/or insufficient heat transfer. Crudded-up engine cooling passages, clogged radiator, improper or stuck thermostat -- that kind of thing.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I recently had this problem. I had just replaced my themostat and a few days later I noticed my temp gauge was over 205 with my cooling fans on. I took the thermostat out and sure enough one side was hung up. Replaced it and havent had a problem since. Just to check yours, take it out and put it in a pot of boiling water to see if it functions properly.

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Old truck: 82 D150 225, 2bbl, dutra duals, 2.5" straight pipe to dual 2.5" tail pipes. Mud tires, 4spd, old forest service truck.
Current truck: 98.5 Ram 2500 ccsb, sport, 24v cummins, 5spd, 4.5" lift, 35's, 5" straight pipe.

Thanks for the help. Tried all including testing the thermostat. I will be flushing out the system soon. Also noticed the cooling fins on the new radiator are not in the best od shape. probably when it was insatlled at the shop it got bumped a couple times. I got a radiator comb and plan on straightening the fins out soon also.

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Billaura1972

Im sure you have considered this already,but
1/Is the temp gauge actually accurate?
2/Remove the cap and inspect the coolant,is there any sign of oily crud floating around or accumulated on the cap? If so this is a sign of combustion leakage,porosity,head gasket,cracks etc.It certainly will make it hot.
3/Make sure the fan is actually drawing air thru the rad,someone may have fitted the wrong rotation fan? (its a long shot,but worth the few seconds it takes to check)
4/When you flush the system,remove the rad and thermostat so you can get a good flow thru the engine,and take a close look down thru the rad cap hole and look at the core tubes,you can only see a few,but if they are showing signs of any blockage,get it cleaned out at the shop,then fit a filter of some kind to prevent recurrent blockage.
5/Check TDC to timing mark,new engine may have an incorrectly marked balancer resulting in incorrect ignition timing.
6/Is the rad core a good quality or a cheapie? How many fins per inch? 2 or 3 row...its all makes a big difference.
7/Air leaks? All the hoses,pcv,booster etc all in good condition?
8/Its a new engine,as you probably know,it will tend to run a little warmer until run in.From my experiences this can take quite a while.I have a smallblock,it was meticuously cleaned,tuned,cooled,fan shrouds etc etc,it still ran a little warm in traffic for 6 months,next summer and 10000 miles later it was perfect...
Good luck with it all,I just thought some of this may be of use to you.
Steve

Well flushing out the cooling system worked. I appreciate all the input.

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Billaura1972