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'73 Charger idle hot, but runs cool when driving down the road; how do I get to idle cooler?

Triple Black 73

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My '73 Charger is running uncomfortably hot when idling, however the engine runs cool going down the road. Please let me know if is would be 'normal' for my setup.

What the temp gauge is doing:
  • Driving: sitting on the far left mark
  • Idling in driveway: straight up
  • In traffic: leaning to the right, but not on the far right mark
  • Outside temp: low 90's
Setup:
  • Engine: 383 stock, 346 heads, 8.75:1 compression, XE256 cam, headman headers, Thermo-Qaud, no AC
  • China eBay Special aluminium radiator
  • right side in, left side out
  • '73 400 left side water pump housing
  • Gates 42032 water pump
  • 2x 12" 1400 CFM fans
  • no fan shroud; fans are mounted directly to the radiator.
  • One fan higher near the inlet; one lower, near the outlet.
  • 180° thermostat.
  • 180° on 170° off fan controller
I'm thinking I need to mount the fans in a shroud with a third 16" 3000 CFM fan pusher set to turn on at 210. Will that get the job done?

I have a new Hayden fan clutch but no fan blade. Should I just put the electrical fans on the front side of the radiator, and mount the mechanical fan on the engine? I didn't do this because I don't like the fan mounted to an engine.

Thanks in advance.
 
Sounds like you aren't moving enough air through the radiator at idle if it cools fine when driving. I prefer to run a mechanical fan but I'm sure someone more familiar with electric fans will chime in.
 
I've seen issues with inferior quality radiators. Install factory shroud, fan & clutch at the very least to start.
 
My recipe is a copper radiator, Hayden clutch fan, shroud, green coolant, 180 Stant Superstat.
Electric fans and aluminum radiators not necessary for adequate cooling. Usa a laser-temp gun to be sure of actual temperature.
 
Last edited:
Put if back like it was when built and you won't have a problem or keep changing what worked,your choice!.
 
Put if back like it was when built and you won't have a problem or keep changing what worked,your choice!.

Dad? Is that you?

Sounds like you aren't moving enough air through the radiator at idle if it cools fine when driving. I prefer to run a mechanical fan but I'm sure someone more familiar with electric fans will chime in.

I suspected this was my issue. Just needed someone to reaffirm it. I just don't like mechanical fans!
 
The factory type clutch fan keeps my 440 under 180 at idle. In traffic. In Reno. At 5000 feet. In August.

Thermal fan has worked for almost 50 years with no load on the electrical system reserved for Garmin, Valentine, AC blower, power windows, dash cam, satellite radio, all which are not original equipment.
 
I'll bet the addition of a fan shroud will solve your problem. Without it, there is no way the fan can create enough flow through the radiator. Start there and I'll bet you solve your issue.
 
I had the same problem with a 73 cuda 440. Stock radiator no shroud. Added the shroud and problem solved.
 
A shroud should help but I'm also curious what your initial timing is. If it's by the book (retarded), it could be part of the problem.....
 
A shroud should help but I'm also curious what your initial timing is. If it's by the book (retarded), it could be part of the problem.....

I was concerned about that to. Currently it's 10 degrees BTC. Anything lower than 8 degrees and the engine won't idle worth a flip, anything higher than 12 and it starts pinging. The idle jets are set at one and 1/2 turns out (give or take). Vacuum is 15 inches. Idle speed is set at 850 in park. Idles a little choppy with the XE256 cam.

I'll bet the addition of a fan shroud will solve your problem. Without it, there is no way the fan can create enough flow through the radiator. Start there and I'll bet you solve your issue.

That makes prefect sense. I read on another thread that the Mopar 7 blade mechanical fans with a shroud draws between 4000 to 4500 cfm. This Derale shroud and fans combo draws 4000 cfms. https://www.summitracing.com/parts/der-16842

Any opinions on it?

Looks like I need to add a laser temp gauge to the BIG LIST ...
 
I was concerned about that to. Currently it's 10 degrees BTC. Anything lower than 8 degrees and the engine won't idle worth a flip, anything higher than 12 and it starts pinging. The idle jets are set at one and 1/2 turns out (give or take). Vacuum is 15 inches. Idle speed is set at 850 in park. Idles a little choppy with the XE256 cam.



That makes prefect sense. I read on another thread that the Mopar 7 blade mechanical fans with a shroud draws between 4000 to 4500 cfm. This Derale shroud and fans combo draws 4000 cfms. https://www.summitracing.com/parts/der-16842

Any opinions on it?

Looks like I need to add a laser temp gauge to the BIG LIST ...
get on ebay, u can buy that for 1/2 that price !?
 
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