383 running hot

[Mike meeks]

I acquired my 66 Coronet station wagon last fall and am still getting a feel for it. It is running hot and my local radiator shop and I am working on troubleshooting it. The guy at the radiator shop says for an engine like this running at 220 is not a big deal but from everything I have read that seems pretty hot. Seems like closer to 190 is ideal. The car has an electric fan (installed by the previous owner) and we realized it wasn't working so we fixed that but that didn't seem to be help much. We have also changed the thermostat (the previous one was in upside down) and flushed the radiator. I have yet to take it on a long drive but in the short trips I have taken, even on the open road, it seems to be running way warmer than it should. Has headers now but I have exhaust manifolds that I am looking to put back on once I get the chance. Thanks in advance for your suggestions.View attachment 966190

You can try taking the impeller out of the housing and Tack welding or riveting a plate behind the fins you take a Round Disc the diameter of the impeller then drill a hole in it slightly bigger than the shaft then cut it in half put it on the back side and take it to the blades or drill and rivet that directs the water much better through the radiator

 

[Sureshot5150]

I acquired my 66 Coronet station wagon last fall and am still getting a feel for it. It is running hot and my local radiator shop and I am working on troubleshooting it. The guy at the radiator shop says for an engine like this running at 220 is not a big deal but from everything I have read that seems pretty hot. Seems like closer to 190 is ideal. The car has an electric fan (installed by the previous owner) and we realized it wasn't working so we fixed that but that didn't seem to be help much. We have also changed the thermostat (the previous one was in upside down) and flushed the radiator. I have yet to take it on a long drive but in the short trips I have taken, even on the open road, it seems to be running way warmer than it should. Has headers now but I have exhaust manifolds that I am looking to put back on once I get the chance. Thanks in advance for your suggestions.View attachment 966190

Have you tried blowing air thru the radiator from the engine side out the front? Could be clogged with dirt and dust not letting enough air to pass thru to cool it.

 

[Bob Cull]

I had a similar overheating problem with my 1967 RB440, A/C car with a Hemi rad. Pressure tested the rad, a small leak was found and re-soldered at the top of the rad where the neck where the neck joins it, still ran hot... 220+. Removed the water pump and replaced it with a flowkooler high flow water pump. Runs cooler 190 - 210 most days except when the outdoor temperature is 30-32+. Then it is up in the 220+ temperatures again.

 

[turbine68rt]

I had a similar overheating problem with my 1967 RB440, A/C car with a Hemi rad. Pressure tested the rad, a small leak was found and re-soldered at the top of the rad where the neck where the neck joins it, still ran hot... 220+. Removed the water pump and replaced it with a flowkooler high flow water pump. Runs cooler 190 - 210 most days except when the outdoor temperature is 30-32+. Then it is up in the 220+ temperatures again.

Do you get any fuel percolation symptoms with those temps?

 

[Stonehengeheel]

Had the same problem with my 440. Was running 195 stat as specd. It was suggested I run a 185. Found a 180 stat, problem solved! Stock fan and shroud.

 

[Cap440]

You could also try water wetter. Just pour in radiator. I think 190-200 max for temp. Is the car hard to re start after it's running hot? Also you can change your waterpump to hv.

 

[bill07960]

Lots of good info. Question what is the source of your temperature readings u say are high? The dash gauge? I’d get a non contact thermometer, mentioned somewhere in comments, and check the actual temperature of the coolant first. Maybe the problem is the gauge. Did anyone mention cleaning the outside of the radiator?

 

[Durandal25]

Sir, I run 383's and 440's here in Texas mid-day in July....in traffic....outside temp 110. Like Kerndog and other have said.....shroud is essential. Also, sending unit calibration too. Do you have a laser thermometer? I use to to check my temp gauge. If you have not flushed the system....do so.....then, make sure all the basic stuff is working. Thermostat, lower hose spring and all the normal heat issues that arise. Also....your fuel system.....you running a spacer on your carb? Is she tuned right? That can have a huge difference....dump the electric fan.....idle heat loading can be an issue with a stock system, but that fan is too small.

 

[70bigblockdodge]

Timing and air/fuel ratio will make a engine run hot at highway cruise. Fin count per inch of tube, cheap radiators have less. Core thickness is another place cheap radiators lack, you can have a 3 core that's 1 3/4" thick and you can have a 3 core that is 2 1/4" thick.

 

[coronetguy]

I acquired my 66 Coronet station wagon last fall and am still getting a feel for it. It is running hot and my local radiator shop and I am working on troubleshooting it. The guy at the radiator shop says for an engine like this running at 220 is not a big deal but from everything I have read that seems pretty hot. Seems like closer to 190 is ideal. The car has an electric fan (installed by the previous owner) and we realized it wasn't working so we fixed that but that didn't seem to be help much. We have also changed the thermostat (the previous one was in upside down) and flushed the radiator. I have yet to take it on a long drive but in the short trips I have taken, even on the open road, it seems to be running way warmer than it should. Has headers now but I have exhaust manifolds that I am looking to put back on once I get the chance. Thanks in advance for your suggestions.View attachment 966190

I had a '66 Coronet 500 but all Mopar big blocks are the same pretty much. What got my 440 to run 20 degrees cooler was a new, (different), water pump. I needed to replace the one that was on the car die to the heater hose connections being welded shut. Just lucky. I put the old impeller in the new housing. Temp dropped 20 degrees. Must have been an internal clearance problem. So buy the best water pump available or go electric.
Also had a 3 core radiator installed. There should be room in yoir radiator to put 3 core innards in it. Also pit a bigger fan on it but watch your clearances to the shroud if still using one. I duhed out and forgot that radiators and motors do not align perfectly and could not use my shroud. Water pump first. Then I could not get the motor above 170 in cooler weather and ran a perfect 180-190 on long highway runs. That is when you know if things are right.

 

[12icer]

You can take the thermostat out of the car and remove the center. Don’t remove it completely or you may have the water blowing through to fast to cool. As for the core size, the bottom tank is what you have to go by in most cases. You can use the top tank on up to four runs most times, but the bottom is the width of the core, and a two run will be too narrow for anything wider. When you have any problems with overheating it is related to flow of air, or flow of water, if you’re using a good radiator. The reason today’s cars use smaller radiators and small electric fans is the heat transfer rate of aluminum is much higher than that of copper and brass. If you have a good Properly sized radiator you should be able to get enough air flow to keep your temperature wherever you want with The right thermostat, and the right fan setup IF as I read in many of the other posts, the water jackets are clean, and you used the right head gaskets.

 

[1967coronet]

You can take the thermostat out of the car and remove the center. Don’t remove it completely or you may have the water blowing through to fast to cool. As for the core size, the bottom tank is what you have to go by in most cases. You can use the top tank on up to four runs most times, but the bottom is the width of the core, and a two run will be too narrow for anything wider. When you have any problems with overheating it is related to flow of air, or flow of water, if you’re using a good radiator. The reason today’s cars use smaller radiators and small electric fans is the heat transfer rate of aluminum is much higher than that of copper and brass. If you have a good Properly sized radiator you should be able to get enough air flow to keep your temperature wherever you want with The right thermostat, and the right fan setup IF as I read in many of the other posts, the water jackets are clean, and you used the right head gaskets.

What 12icer has posted about {the correct head gaskets } is more important than guys think it is.
My felpro gasket set had the blue seal head gaskets, The dog bone shaped water passages from head to block were only just a small slit on the gaskets. I took a razor blade and enlarged them to get more flow, That and the flush with evapo rust I think helped a lot.

 

[ChiCy]

I have a friend with a 73 charger 400 motor. Fresh rebuild from previous owner. Ran hot, really hot, boiled the radiator over. Replaced the stat, still hot. Radiator flowed good. Tried electric fan, still hot. I put in a good brass stat and it never got over 190 on a hot day. Even took the electric fan back off and put it all stock.

 

[ChiCy]

What brass thermostat would you recommend? Also, what radiator cap is best? Thanks again

 

[ChiCy]

All great suggestions. Just need to keep checking all these suggestions until I sort it out. In any event I’d like to go back to stock fan and shroud. Any suggestions where to look for these items?

 

[ChiCy]

220° is getting warm but not overheating. You didn't mention what degree t-stat you put in. Try a 180° and make sure your cap is good. I know fan blades are a power drain but they are quite efficient and with a shroud they can be even more so. A thermostatic clutch operating properly doesn't take much power until it locks up. Most drag racers don't use them. The electric fans are easier to control but you could use more fan. Your single fan, regardless of how much air it pulls, only covers 1/3 of the core. You need another one at least. Something like this would be good. Late model fans from the salvage yard may be good choices as well.

View attachment 969930

Where is best place to order a fan like this? I agree, now that it has been pointed out by the group my current fan covers less than 1/2 of the radiator.

 

[diesel_lv]

What brass thermostat would you recommend? Also, what radiator cap is best? Thanks again

I run a Mr Gasket 4367 180° thermostat. It is all brass just as the original Robert Shaw. My 496" stroker in 110° temps on flat n level w custom dual electric fan shroud runs 195 and on a grade at 60 mph runs 200-205. That's with a/c on max. Thermostat works perfect. As for factory fan clutch, fan n shroud, you can find a close copy of the fan at Flex a lite or Hayden and the fan clutch at Hayden. The shroud will either be used or possibly from someone like year one.

 

[diesel_lv]

Here's my fan set up. 1 Spal 13" 1750 cfm fan, 1 (cut from factory shroud) Ford Contour fan in custom shroud covering entire radiator. Then 10 - 2 inch holes with rubber flaps over them. Allows full airflow while cruising and allows fans to pull all air through full radiator surface at slow speed/idle. A/C froze me out while idling for 20 minutes waiting for an accident to clear in 110 temps yesterday. FI computer showed engine get to 208° max during that time. So I think they are working well.

 

[ChiCy]

220° is getting warm but not overheating. You didn't mention what degree t-stat you put in. Try a 180° and make sure your cap is good. I know fan blades are a power drain but they are quite efficient and with a shroud they can be even more so. A thermostatic clutch operating properly doesn't take much power until it locks up. Most drag racers don't use them. The electric fans are easier to control but you could use more fan. Your single fan, regardless of how much air it pulls, only covers 1/3 of the core. You need another one at least. Something like this would be good. Late model fans from the salvage yard may be good choices as well.

View attachment 969930

Looks like he installed a 160 degree thermostat. Is that a good option? I’ll look into a new cap. Thanks again

 

[diesel_lv]

Looks like he installed a 160 degree thermostat. Is that a good option? I’ll look into a new cap. Thanks again

As has been stated many times in this thread, the thermostat sets the minimum temp an engine will run at, not a max. Airflow, radiator efficiency, waterflow set max temp. I live in normal 110-120 degree temps for 5 months out of the year and a 180 in my 610 hp 496" engine works perfect. A 195 in my heavy '87 K5 Blazer in these temps with factory fan, fan clutch, shroud and radiator works perfect. As for a cap, it depends on your radiator and what it's pressure rating is. I use a 16 lb billet cap that came w the radiator. But I use an ACDelco on my Blazer.