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Engine runs hot in slow traffic

Eric F

Active Member
Local time
6:40 AM
Jan 22, 2023
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Atascadero California
70 Road Runner 383 .060 9.3 compression. Mopar aluminum water pump housing with 8 impeller water pump. 180 degree thermostat.
‘my car originally 22 inch 3 core radiator with a solid fan and shroud. When I put my car together after sitting apart for 27 years. The engine was rebuilt. I installed a Champion 22 inch 3 core radiator with a fan and shroud I also used a Hayden thermostatic fan clutch and 7 blade fan from a motorhome. First warn cruise night it got to 230 within 20-30 minutes. I pulled out of cruise night boom cools off to about 200 within 10-15 minutes of driving. I added a flex a light 1850 cfm pusher fan. It helped brought the temp down to about 225.
I then decided to try a 26 inch 2 core radiator also installed a fan shroud same fan and fan clutch. Note I did NOT cut the radiator opening as it is numbers matching car and a somewhat rare color. I found that the 2 core radiator and with the pusher fan it’ll maintain 220 in slow speed traffic on a night above 90 degrees. I had a mishap and the fan shroud came loose the fan hit the shroud destroyed the shroud, bent the fan. I took apart the cooling system I also found that the impeller slipped on the water pump shaft.so with the car apart I back flushed the block just for good measure. I had a hi flow water pump in my stash. Its a 440 source 40 gpm pump. I installed a solid fan I had laying around off a C body and installed my 22 inch 3 core radiator ( I flushed the radiator before installation) put it together. I started the car up was doing some testing and noted the solid fan has little are flow just wasn’t pulling much air. Ok. I ordered and Hayden fan clutch as mine might have been damaged I also ordered and installed a Derale 6 blade high cfm fan blade. Got the car running and noticed quite a bit of air flow. Great. Took it around town and did good but outside temp was around 60 degrees.
yesterday was an above 70 degree day and took the car out for the day. I noticed driving speed about 15-20 mph and above the car runs and stay around 180-185 perfect. Went through town and got up to 225 because I was going 10 miles an hour. And I was creeping to the 230 mark.
im puzzled at why my can maintain better cooling temps with a 26 inch 2 core radiator with 4 inches of core blocked than a 3 core 22 inch radiator. Possible there are too many cooling tubes and there is not enough air flow past the tubes?
is you fan at least 1/3 out of the shroud? Its all about the shroud and fan ,not fan to radiator.
Have you verified that your temperature gauge is correct? What is your timing set at?
agree with pnora, I run a mechanical temp on my Bee. Factory gauge is off by 15 degrees.
Low temp cooling problems are usually lack of shroud or too small a fan. Try a high flow thermostat too, opening in the stat should be 1 7/16"
Yeah, something is not right. A factory 22" radiator will have no problem cooling a 383 as long as everything else is up to snuff. I have a 22" oem radiator that was redone by Glen Ray in each of my B Bodies cooling 570 and 590 hp stroker motors.
What pulleys are you running? On my 440 I have under drive billet pulleys. I bought them by accident and the instructions warn about heating issues
Have you verified that your temperature gauge is correct? What is your timing set at?
Yes running a mech gauge and factory. Also verifed temp with my snapon thermal imager temp gun. Timing is at 12 total 36. It doesn’t matter if I more or less timing
I bought the car apart. I had no radiator. No fan nada. I had to build a cooling system
Was just going by what you wrote in the first post!

My 383 Bee doesn't even have a shroud. Factory correct 22" radiator and 7 blade fixed 2863 224 curled tip fan. 180 stat and it runs 185 on the highway and 200 tops cruising town hard in first and second gear. My 5 other cars all run similar on correct OE radiators. 4 of those, including the Hemi, have the same fan.
could the pusher fan be blocking air flow at low speeds? We are all trying to help/explain a factory set up will keep your engine cool.
I bought the car apart. I had no radiator. No fan nada. I had to build a cooling system
At a 500/600 rpm idle will a dollar bill stay stuck to the grille ?
If not it is a air flow problem.
If it will you most likely have a coolant flow problem.
You mentioned some 440 source parts.
At one time they did have a batch of pump housings that had flow issues.
How many years of crud is in the block and heads ? Evapo rust makes a real good rad flush.
Since your car seems to cool off at road speed it's prob a air flow deal.
Car was apart when I bought. There was nothing. No radiator, no fan no pulleys. Nothing.
Oh, ok. Then just install a factory setup. Glen-ray radiator, fan, shroud. Worked then, will work now. If not, you got another issue.
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