OVERHEATING

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Franko

Franko

FABO Gold Member
FABO Gold Member
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Jackson, Mi
When I drove my 1969 Swinger 340, 4 speed, with a 3.55 rear end gear, on the expressway at 75 mph (3,500 rpm), it overheated at 220 degrees, in only 2 miles. Driving on back roads at about 45 mph, the temperature gauge always remained at about 180 degrees.

The 340 was rebuilt a couple of years ago and has 2,800 miles on it. It has the following stock engine parts:
heads, cam, (9.7:1 C/R), intake, AVS carburetor, rebuilt water pump (No. 2863067- 8 vane- for non-AC).I purchased a stock water pump pulley (6 1/2”) and a stock crank pulley (6 1/8”). It also has a fan shroud, clutch fan, 16 lb radiator cap and a 180 degree thermostat.

Then, I had the stock radiator (No. 2949066), re-cored (3 row) by Glen-Ray. It still overheated at 75 mph. Next, I replaced the 180 degree thermostat, with a Robert Shaw/Stewart High-Flow 180 degree thermostat and installed a coil spring in the lower radiator hose, in case it was collapsing at 3,500 rpm. The only improvement was that it took 10 miles to overheat instead of 2 miles.

My engine builder wondered if 3,500 RPM is too high to cruise on the expressway. But it seems that turning 3,500 rpm with a 3.55 would have been normal back in the 60s.

I read the following in FABO: “The other thing to consider is that Mopar and their testing came up with an idea that the eight blade might cavitate at really high RPM”.

Mopar Action (Rick Ehrenberg) stated “the enemy is not heat, but boiling, especially localized steam pockets in the cylinder heads…use a surfactant such as Red Line Water Wetter…”

Muscle Machines (Ask Ray) stated “providing a pulley ratio of at least 1.25:1 relative to crank shaft speed…a RobertShaw balanced -sleeve 160 degree F thermostat and, most important, Evans NPG+ coolant”.

Any thoughts about cavitation, pulley ratio, switching to the six vane AC water pump, Red Line Water Wetter, NPG+ coolant or a 160 degree thermostat?

Thank you for any comments.
 
When it's really hot , shoot the temps of the actual metal fitting top and bottom rad hoses.
You need min 30* drop, 50* would be better .
If you don't get a decent drop, shoot areas of the rad looking for cool/cold areas, those areas would be plugged, perhaps at manufacturers.
You just about done it all .
Good luck .
 
Franko said:
Any thoughts about cavitation......switching to the six vane AC water pump
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No way on switching from 8 to 6. If your current pump does not have the anti-cavitation plate, and originality is a concern (I assume as you had it rebuilt) I would install a plate on the vanes. Otherwise get a Gates or similar 8 w-plate.
 
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First thing that jumps out at me is, your water pump is being under driven.
 
Many things cause overheating, when you're driving 75 mph you have enough air flow into the radiator the fan is not needed unless driving up a hill. Is the radiator sealed to the core support to force air into the rad and as inertia stated you need to check for any cool spots in the rad with a tool or light touches from fingertips. When you were driving did you hear the fan clutch roaring? I would use a 160 t-stat.
 
moparlvr166 said:
I would use a 160 t-stat
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IMHO 180 thermostat is wide open by 190 for sure so no reason other than coolant flow or air flow to cause overheating.

160 thermostat only sets the low temp has nothing to do with regulating the upper temp once it is fully open say at 170
 
Dana67Dart said:
IMHO 180 thermostat is wide open by 190 for sure so no reason other than coolant flow or air flow to cause overheating.

160 thermostat only sets the low temp has nothing to do with regulating the upper temp once it is fully open say at 170
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Well.......sorta. In some cases it CAN HELP the overall upper temperature by opening sooner and stopping heating up sooner. It did in the case of my slant 6, but you are overall correct in that in general, the thermostat does not control max temp, but the minimum temp. I also think in my case, that changing to a high flow thermostat helped too. Since I went with the 160 high flow all at once, it's difficult to tell "which" attribute helped. In a good hot engine though, it cannot hurt a thing to run the 160. Just tune for it and you'll be fine.
 
Dana67Dart said:
No but my point is that while his is under driven by 5 percent it was done on purpose to stock engines.

Not saying it's good or bad in his case.
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I understand, but TODAY he has to put up with crap ethanol fuel which can aid in over heating. So with his "hotter than your 273 340", he can run into problems.
 
In my experience. 340 9.8 cr with aluminum heads and EFI, I run right at 180. I have a flowcooler high flow wp and Robert shaw 180 high flow thermostat, Champion 26" radiator.

Anyway, I've found that a high flow stat does nothing without a high flow pump.
 
plumkrazee70 said:
Anyway, I've found that a high flow stat does nothing without a high flow pump.
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It certainly did in my case. This was on my fairly hot slant 6 though, so this might not be a good comparison to V8s.
 
Did it overheat before the radiator was done with a new core. I had the same issue and pulled my hair out trying to find it. It was Air flow. At that speed you don't need a fan.

My radiator tubes were bulged. Could have been from being over pressurized Possibly from the shop that installed the AN fittings or from freezing. I had no air flow . Hold a light behind the rad and look through. Or hold paper in front while its running. 5000 stall, 456 gears, never went above 180 cruising a 60 mph. after installing a new radiator.
 
Oldmanmopar said:
Did it overheat before the radiator was done with a new core. I had the same issue and pulled my hair out trying to find it. It was Air flow. At that speed you don't need a fan.

My radiator tubes were bulged. Could have been from being over pressurized Possibly from the shop that installed the AN fittings or from freezing. I had no air flow . Hold a light behind the rad and look through. Or hold paper in front while its running. 5000 stall, 456 gears, never went above 180 cruising a 60 mph. after installing a new radiator.
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Yes! I had a radiator that had weak fins do to old age . They would close up (bend shut a little) at highway speeds and overheat. No problem with overheating at 45 mph. My vote is air flow for one reason or another is your problem. Like OMM said.
 
Franko said:
Any thoughts about cavitation, pulley ratio, switching to the six vane AC water pump, Red Line Water Wetter, NPG+ coolant or a 160 degree thermostat?
Click to expand...
I took the fan clutch off and installed the mechanical fan solved all of mine, "it seems to run too hot", problems...
 
On my 78 Fury,I had to replace the water pump a few years ago, under 50k miles "first time around" the odometer. Age got it not miles.
Anyway the first thing I noticed when I took the original one off and took the replacement out of the box was that the original had 8 vanes, the replacement had only 6. At the time I questioned the parts house, and was told "that's how they all come now a days". Bull$#it.
But I took them at their word at the time and that difference in water pumps took that thing from a car that never overheated to one that overheated every time I drive it over 45 mph. No other changes besides the water pump.
I've since re replaced the water pump with a"flow kooler" one and no more overheating. . I've even more recently replaced the original radiator with a 3 row champion (no way I was putting a Toyota -ish plastic/aluminum pile o' **** in my car) and a 180* stat and it runs too cool now.... Back to a 195 for me. This is a stone stock 318-2 bbl that even still has the lean burn.....
 
Unless I missed it, nobody has mentioned ign timing. Retarded ign timing will very quickly cause o'heating. Make sure your dist centri weights are moving AND that the vac adv unit is working.
Failure of either/both will cause hot running.
 
I dealt with a similar situation yesterday.
1970 Charger 383 4 barrel. 2 row Griffin radiator. Clutch fan. No shroud. 3.91 gears.
I've driven the car with 150 miles on the rebuild all around the local area and have not had a problem with getting too hot. Burnouts, full throttle runs, idling in traffic, cruising, etc.
A friend was driving it Yesterday on the freeway, 15 miles in, it pegged the gauge so we pulled into a gas station. It took a lot of time and water to cool it down. A short time later while idling in line at a car show, it shot up again.
I removed and tested the thermostat. It opened when before the water boiled so it wasn't stuck shut. I replaced it and the water pump but I don't know if that was the problem.
In theory, freeway speeds should provide more than adequate airflow through the radiator but if there is some internal blockage of coolant flow, a slipping fan belt or clutch, too little ignition timing or an excessively lean fuel/air mixture, it may overheat.
I'm still unsure of what caused mine to boil over.
By the way...I agree with Wayne....220 isn't ideal but it isn't what I'd call "overheating". To me, that definition should be reserved for a condition where the radiator is puking into the overflow tank or onto the ground. Straight water boils at 212 degrees and a pressurized system raises that up quite a bit.

Coolant_Temp_VS_Pressure_Chart_1024x1024.jpg
 
My distributor was locked at 36 Degrees BTDC. The ignition box would retard it 20 degrees for start up . As soon as the engine reached 800 RPM's it went to 36 degrees BTDC.

I tried everything Twin electric fans, Electric water pump, Moved the cap to the engine, Bleeder in the pump. Large Oil cooler with remote filter. Large trans cooler. Air scoop under the bumper to direct flow, Sealed the air breather to the hood. 3 1/2 inch exhaust with 2 inch tube headers.

I didn't think radiator because it was a becool good for 1000 HP. and it was $800 . After I bit the bullet and put a new radiator in the car I had a hard time getting heat in the engine. I cut the old radiator in half and every tube was bulged that they were touching.

Had the radiator in for one season and the car was smashed and destroyed the radiator. I had to buy a new one for the new car, Now we are not using it or the new fans, Or the coolers. We are going to a smaller radiator off to the side and putting the fuel tank in the front on the other side.

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Oldmanmopar said:
My distributor was locked at 36 Degrees BTDC. The ignition box would retard it 20 degrees for start up . As soon as the engine reached 800 RPM's it went to 36 degrees BTDC.

I tried everything Twin electric fans, Electric water pump, Moved the cap to the engine, Bleeder in the pump. Large Oil cooler with remote filter. Large trans cooler. Air scoop under the bumper to direct flow, Sealed the air breather to the hood. 3 1/2 inch exhaust with 2 inch tube headers.

I didn't think radiator because it was a becool good for 1000 HP. and it was $800 . After I bit the bullet and put a new radiator in the car I had a hard time getting heat in the engine. I cut the old radiator in half and every tube was bulged that they were touching.

Had the radiator in for one season and the car was smashed and destroyed the radiator. I had to buy a new one for the new car, Now we are not using it or the new fans, Or the coolers. We are going to a smaller radiator off to the side and putting the fuel tank in the front on the other side.

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Ouch, poor car! Sad when our old girls get hurt. I too had a be cool radiator on my car years ago. Never could get it to cool properly. Very frustrating to put "good" parts on a car and have this sort of thing happen.
 
Spark plugs do three things. They provide spark, keep themselves clean and they PULL HEAT OUT OF THE COMBUSTION CHAMBER.

Start two steps colder.
 
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