1939 Ford flathead belt size

[mr_charles]

Hi again everyone!

Quick question:
What fan belt size would be correct for my 1939 Ford flathead? The belt would cover both water pumps, the generator, and obviously the crankshaft. I tried measuring the old one and I got around 53 inches, but it’s a bit worn and not the most accurate. I saw some 52 inch ones online and was wondering would those work?? Let me know what you think is best.

Thanks!!

[cadillac512]

Most common is a B51, which is 54" long. (B series belts measure 3" longer than their part number)

[ssffnomad]

Caddy , that’s why we come to the FordBarn.
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[russonator]

Originally Posted by mr_charles

Hi again everyone!

Quick question:
What fan belt size would be correct for my 1939 Ford flathead? The belt would cover both water pumps, the generator, and obviously the crankshaft. I tried measuring the old one and I got around 53 inches, but it’s a bit worn and not the most accurate. I saw some 52 inch ones online and was wondering would those work?? Let me know what you think is best.

Thanks!!

Apparently there is no one answer to this question. Depends on model and valve chamber cover composition (alum or cast iron). Here's a chart from the EFV8CA 38-39 Ford Book:

[petehoovie]

Originally Posted by russonator

Apparently there is no one answer to this question. Depends on model and valve chamber cover composition (alum or cast iron). Here's a chart from the EFV8CA 38-39 Ford Book:

[russonator]

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[Flathead Fever]

I keep a bunch of cut belts. I set the generator or alternator down to its lowest point on the engine and then take a cut belt and wrap it around the pulleys and take a measurement of the length, maybe add just a little to it. That usually works out pretty good by the time I tighten it up. The local stores should be able to sell you a belt based on the length and if you need a little more of less you can return it and swap it out.