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#123693 - 07/17/08 06:08 PM Fan to Radiator Clearance
Rusty 37 Master Offline
Backyard Mechanic

Registered: 12/29/07
Posts: 226
Loc: Iowa
I re-installed the radiator and a new after market water pump on the '37 coupe this afternoon. The clearance between the fan blade and the radiator is only about 1/4". It took a lot of finesse to install the belt. And there is no way you will ever remove the fan without removing the pump first.

Is this normal? The fan is not quite parallel to the radiator, but this does not surprise me. This is the clearance at the closest point. I measured it at the tip of a blade pointing straight up.

Yes, the fan was extremely close to the radiator before I took everything apart. The after market pump that was on the car actually had a spacer for the fan mounting that was labeled "For 1938 car only". I was thinking I would get a little more clearance with this new pump.

Thanks,
Rusty
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Rusty

VCCA #44680

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The Filling Station 1937-42
#123696 - 07/17/08 06:53 PM Re: Fan to Radiator Clearance [Re: Rusty 37 Master]
Chev Nut Online




Registered: 01/08/02
Posts: 19400
Loc: West Allis,Wi.
There were several changes in the 1937 water pumps. The original still had a packing and two oilers. From what I have read these had a very short life. The early 1938 had a version of that pump. The late 1938 had a sealed bearing pump with a modern internal seal. The late 1938 pump ended up being the replacement for both years. When the late style pump was installed on a 1937 a different fan blade was required, ...Fan blade part #838933 was required on a Master DeLuxe and 838936 on the Master. The Master DeLuxe fan would be my choice for the Master as it had narrower blades and produced less fan noise. The 1939 water pump was the same as a 1937-38 (replacement) but had deeper (longer) pulley. You may have a 1939 pump. If I remember correctly the original 1937-38 fan had a center "spider" and the blades were riveted onto it. The other pumps had just the two blades riveted to each other in the center area.
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Chevgene

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#123821 - 07/20/08 01:36 PM Re: Fan to Radiator Clearance [Re: Chev Nut]
Rusty 37 Master Offline
Backyard Mechanic

Registered: 12/29/07
Posts: 226
Loc: Iowa
As always Gene is right on the money. I really appreciate his willingness to share his knowledge.

Like Gene said, there was an evolution of pump design. The first change was to make the housing and shaft 1/2" longer to get the bearings further apart. That might not sound like much, but this reduced the bearing load by at least 15% due to the increase in distance between the bearings. The disadvantage was that it moved the front end of the pump 1/2" closer to the radiator. The second change was to use an improved bearing design in the longer pump. The longer pump required what the parts catalog calls an "offset" fan. On the longer pump the distance from the back of the pulley to the front hub is 2 3/4".

Now I'm trying to figure out if I have an "offset" fan. It is a 2 piece design with the blades spot welded to each other. It is 16 1/4" in diameter with a 1" hole for the pulley hub and a 2 1/4" bolt circle. I'm thinking it is #838936. About a month ago I saw an original '37 fan at Classic Cars of Williamsburg. It was a multiple piece design with the blades welded to a center hub. There were actually small angle pieces welded as reinforcements to the flat blades. There are stiffening ribs stamped into the blades of the fan I have.

I'm coming to the conclusion that the fan just runs that close to the radiator. Sort of scary if the engine moves around much at all.
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Rusty

VCCA #44680

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#123835 - 07/20/08 04:51 PM Re: Fan to Radiator Clearance [Re: Rusty 37 Master]
Chev Nut Online




Registered: 01/08/02
Posts: 19400
Loc: West Allis,Wi.
I did some more digging in books as well as in my memory. You are correct, the 838933 (15 3/4") or the 838936 (16 1/4"-wider blade) would be the correct replacement blades if the later 1937-38 Chevrolet brand water pump is installed. Back in the old days when I dug through parts stock used to find these all the time.
The original 1937 blade was the two blades riveted together type. The blade with the spieder in the center was used for 1938, early cars with the oiler type pump. I can'temember if the 838933-936 had the spieder or not but I would be sure some of these blades are laying around some place.
_________________________
Chevgene

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#123847 - 07/21/08 12:45 AM Re: Fan to Radiator Clearance [Re: Chev Nut]
Lou Offline
Backyard Mechanic

Registered: 01/05/02
Posts: 414
Loc: Berkeley, Ca.
Be sure your motor mounts are in good condition or your fan will eat a hole in the radiator. The closer the fan to the radiator, the better the cooling.
I put an optional 6 blade fan on one of my ton & half trucks and the mileage dropped 12%. It sang the whole trip. I put a 1950s style 4 blade back on with a shroud and got better cooling and mileage went back to 20 MPG.




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