VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1941 Chevy Coupe w/1956 235 ci OVERHEATING Problem

Just read 'Fan Frenzy - Swap in a truck fan to keep your cool' submitted by Phil Lipton, in the September G&D.
I have a similar overheating/cooling problem with my '41 Chevy coupe with a fresh, professionally rebuilt '56 235 ci engine and a newly re-cored, stock, '41 Chevy radiator, and currently not using a thermostat. I am also running a '53/'54 water pump using an 'adaptor plate' which positions the water pump and the stock '41 passenger-car fan blade dead center on the '41 radiator.
I, like Phil, ran a test using a large 'shop fan' placed in front of the grill/radiator, and found that the big fan cooled the hot engine (195 deg - at idle) down to 175 deg fairly quickly, and then maintained that temperature.
The folks at Walker Rediators had previously suggested I run a test (just like Phil's) to determine if the cooling problem could be a result of a lack of airflow. This test proved that was indeed the case and that additional airflow would be a better solution than installing a larger radiator.
I don't have access to a Chevroelt Parts Book, so I'm asking if anyone out there could provide me information from an official Chevrolet Parts Book as to the specifications (sizes, part numbers, etc.) of commercial fan blade applications from 1941 through 1954 so I can then go online to hopefully find a NOS truck fan blade. Also, if anyone has such a fan blade which I could purchase, that would be great too!
Thanks in advance for any help you might be able to provide.

Roys41

First of all, put a thermostat in it, then run the engine at least 500 miles to loosen it up. Driving down the road should put as much air through the radiator as the test fan you are using. It is not unusual for a newly rebuilt engine to run hot until it breaks in a little bit. A 180 degree thermostat will probably help. I don't know what truck fan will work. Some have too much pitch to clear the radiator on a passenger car. I am running the same engine as you are in my '48 passenger car and the stock fan off the 216 engine seems to work just fine for me.

First the repositioning of the water pump may be a part of the problem. The 1955 and up water pumps set into the block, had a larger impellar, turned 1/3 slower as did the fan. The fan was increased to 17 inches and had more blade pitch. Also larger inlet and outlet passages (hoses) were increased in size for increased water flow. In original form these engines were very well cooled.
Now to the fans.
The standard fan was part #838277 and was 15 3/4" in diameter. It was used from the late '30's to 1954 with one exception.
The "heavy duty" passenger car fan, 838279, was 16 1/4" in diameter with wider blades. It was for heavy duty cooling and also used on 1938-1949 cars with the optional 3.73 axle ratio (engine worked harder on hills, etc). It was noiser than the standard fan
The truck fan was 839020, had 18" very wide blades and was very noisey.
Was used on all sized trucks from 1939-1954.
There was also a heavy duty truck fan, 604225, with 6 blades listed for low speed operation....talk about noisey.

If needed I have a new 838279 H.D. car fan.

Also the 1938-1954 truck fan is a larger jump from your present fan than the 1935 car fan was from the 1935 truck fan.

Thanks very much for your quick response. Perhaps I mis-spoke about just how 'fresh' my engine rebuild and radiator re-core job really is: I now have put 2,325 miles on the completely refurbished drive train, so I think it is probably broken in. I have significant recent mileage with and without the 180 deg. thermostat and it makes absolutely no difference to the operating temperature of the engine once it is warmed up. This is the San Francisco Bay Area I live in after all - and we just don't know cold here!
I have found that cruising at or above 35mph, with ambient temperature at 80-85 degrees, the operating temperature of the engine runs at 175-180 degrees. However, when I have to slow down for city stop-and-go traffic, with frequent periods of simply ideling in traffic - and we have a lot of this condition in the San Francisco Bay Area, unfortunately, the engine temperature climbs up to the 190-195 degree (red) mark on the Temp Guage. Once I can resume a consistant 35mph+ cruising speed the temperature drops back to the 175-180 mark. Also, when I park the car after curising at 35mph or so the temperature climbs up to the red mark. But again, as soon as I can resume my comfortable cruising speed the temperature returns to the 175-180 mark.
I have verified the accuracy of the NOS Temp Guage and it is right on the money. I use an infrared temperature sensing tool to check the temperatures of the cooling system and engine - what a neat tool that is!
You may very well have a point about a truck fan having too much pitch. I'll just have to see if it works out once I get the truck fan.
I do have a question about your situation: are you running a ''53-/'54 water pump' with the special adaptor plate, along ith your stock '48 fan blade? I was advised to run this combination because the stock '56 fan would be mounted too low in relation to the center of the radiator, and the adaptor plate positioned it correctly in the middle of the radiator.
Thanks again,

Roys41

The temperature ranges you are experiancing are quite "normal"
These cars just get hot at idle in warm weather. Also common to "hit the top" when engine is shut off.
A truck fan is wirth a try and let us know what the results are.
Perhaps you could find a used fan for the experiment.

Thanks Gene for the quick response.
I debated whether to run a '56 water pump, with a specially 'shortened' pully shaft and the stock '56 fan. The fella I bought the '56 engine from allowed as how I might have 'clearence problems' with the stock fan and the vibration dampner (because of the shortened shaft) and that I might have to tweek the fan blades to clear the vabration dampner. I didn't like the sound of tweeking the fan blade, and furthermore, I had heard of the 'special adaprter plate' allowing use of a stock '53/'54 water pump enabling the use of my stock '41 fan blade, which positioned the fan 3 1/2" further up at the center of the radiator (than would be the case using the '56 water pump). So I was a bit unsure if I could even have used the '56 short-shaft pump and '56 blade.
As for your mention of the large inlet passage: I'm currently running the stock '41 top radiator (hose) inlet with a (1 1/4" dia.) as well as the stock '41 thermostat housing, (with a 1 1/4" dia. hose); plus using the stock lower radiator (hose) outlet (which is 1 1/2" dia.) along with the stock '53/'54 water pump outlet (which is 1 1/2" dia.)
I have thought about having thI larger (1 1/2" dia) upper hose neck installed on my radiator coupled with the stock '56 thermostat housing (with a 1 1/2" dia.) hose neck. If I do this I'll also have the shop install a neck which will accomodate a 7# pressurized radiator cap.
I am using a repro '41 Chevy Radiator Overflow/Recovery Tank. I'm running a 50/50 mix of 'Peak' All wether Coolant and distilled water in the system.
I am very interested in your "heavy duty" passenger car fan, part #838279. This certainly would be the simpelist 'fix' if in fact it does the trick. Does it have a 1" dia. shaft hole and a 2 1/4" bolt circle? And what is the diameter of the fan blade?
If you are willing to part with it I'd be ever beholdin' to you. Let me know the details.
Thanks again Gene for your expertise and your willingness to share it with one and all. You are greatly appreciated!

Roys41

I have that same water pump adapter on a 57 235 that is in my 37 p/u and it will not go past 180 on a 90 plus degree day,yes you do need a thermostat as it will keep the coolant from flowing too fast and allowing the coolant to do its job and absorb the heat from the motor. I do see the six blade truck fans on ebay occasionally but put the thermostat back in and allow the motor to break in while driving at some speed so the air will flow through the radiator.

I have those same numbers on my heat gauge for those various conditions, in my 38 Master with the 40 216 motor.