I read through previous threads on this subject but didnt see the answer to my question so any help would be appreciated. I realize the size should be 3/4 for my 49 F1 8BA pulleys but all the replacement water pumps come with 5/8 pulleys. My crank, generator and fan pulleys are 3/4s and I do not have the original water pump pulleys. I plan to run the shorter 3/4 belt from crank to fan. Has anyone run the 5/8 belts across the crank, generator and water pumps? Or did you run the 3/4? Or did you swap the WP 5/8 pullys for the 3/4?

 

'51-on Car pumps are 5/8", Truck pumps are 3/4". If you look at pumps with 5/8" sheaves, look at the motor mount area. They won't have the "foot" like truck pumps. Cars from the '30's thru '50 were the same as trucks.

 

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Its hard to tell from pic but these are RT pumps with the foot to mount to the motor mount. I will send another pic in a bit when i get home.

 

Yes, I can see the mount, they are truck pumps. Car pumps almost completely lack a foot.

Where are you seeing Truck pumps with the narrow belts?

 

The part number for the pumps are 8RT-8501 and here is a link from DC:
Water Pump - Right & Left | Dennis Carpenter Ford Restoration Parts
which specify 5/8 Wide Belts for 1948-52 truck. Do you know of another part number for the water pumps that would come with the 3/4 pulleys?

This is a 3/4 belt on the 5/8 pump. Please note the pump foot on motor mount.




Measuring the pulley, looks like 5/8

 

Sure does look like 5/8 at the sheave, but the 3/4" belt doesn't look wrong on it either. They do stick out a ways. Let's see what others who run the fat belts say (I run the Car belts, long story). NAPA shows a belt that is closer to 5/8, too.

https://www.napaonline.com/napa/en/p...544_0117360645

 

I've searched all shops that I could and they all sell the 8RT-8501 Truck WPs with a belt width of 5/8, which is the WPs that I have. Yet my crank, fan, generator measure 3/4. I assume others are using these pumps on their F1s? I can't imagine swapping out all your 3/4 pulleys to match the WP 5/8. Maybe I need to find some original pumps and swap my wp 5/8 pulleys for the original 3/4 pulley.

 

Do you have the old belts? I just measured the WPs, generator, and crank pulleys on an 8RT, and they are the same as yours; 5/8" on the WPs and the others are more like 3/4.

 

Unfortunately I dont have the old belts. So what belt width are you running on the WP, crank and generator? The 5/8 width 54.5 length belt?

 

I can't help in that regard, because my engine uses the narrow (Car) belts. The Parts books all say you should use the 3/4, I'd try it.

 

I'm using 5/8 belt on mine, no problem. The other pulleys have enough depth. My flatty has aftermarket pumps.
Narrower belt needs to be slightly shorter.

 

Thats good to know about the narrower belts needing to be shorter. I figure I will try the 5/8 belt around the crank 3/4, gen 3/4 and WPs 5/8. I will keep the fan and crank at 3/4 since have the 3/4 belt already.

 

well after much deliberation (in my head) I went with an 11/16 width and 53 7/8 length belt from Napa. I figured its a bit bigger than the 5/8 and still smaller than the 3/4 which sits better in the WPs. Im still a few months from firing it up so we will see how it goes.

 

I didn't know they made belts in 11/16! Should be fine.