I dont know the length but I think it is what I refer to as an "A" section about 5/8" (16mm) across the back where the common belt on 1960 and later models use a 1/2" (13mm) belt. To get the length take the adjustment as far in as it will go and put a tape measure around the belt path, this circumference is the number you need (an A24 belt is an "A" section belt 24" around for example).

Tony 

@neil-fullwood Good morning Neil. You might find a piece of string will be easier to wrap around then measure than a tape measure. I wasn't as smart as Tony when I was finding belts for my 38 and ended up making several trips to the parts store. During that saga I did find that a 1" difference in length makes a large difference in fitment of the belt. If your measurement comes out to be between inches (for example 24 5/16") I would buy a 25 inch belt.

@anthony-williamson 

Hi tony

Respectfully, the belt Neil is looking for should be a standard "B" v-belt.

Standard B belts are 21/32" wide, which is just over 5/8".

Many many old vehicles (including Chevrolet sixes and apparently Model A Fords) used a B-40, and I know that is what fits '46 Chevs.

I believe it was Gene who said that many years back a small store could stock just B-40s and satisfy the vast majority of customers looking for a fan belt.

PS

And the number on the belt will be the INNER circumference, so using a string as Tiny recommends will get you the number you need.

My (just sold) 24 had Gates number 22320 on it but I thought it was too loose but it was working. Since there is no adjustment on a 24 for belt tension I bought a Continental 22310. Which measures .69 by 31 inches, 38 degrees. I did not get around to trying it so it went with the car. I presume the 32 in 22320 is also inches.

Dave

This is the fan belt you need. This is what I have had on my '25 sedan for over 20 years. You have to slip it on by turning the engine crank by hand to go over the pulley. You can get it on Ebay for $20 with free shipping.

Looks like that fractional hp belt is 31 inches and should work. I have also used the green mower belts but you can get the black in the same size.

Dave

I have not had success measuring the bottom of the "V", nearly always have 2 trips to the store.

Tony

@anthony-williamson 

Hi Tony

There are a couple of things you need to take into account with v-belts.

First, as you know they never run on the bottom of the groove in the pulley, so after you measure around the bottom of the grooves you will need to add up to a few inches depending on how many pulleys you are going around and what type of v-belt you are looking for.

Second, standard or conventional v-belts like the A series and B series are measured and labeled by the INSIDE circumference.  Fractional horsepower belts like the 5L series, and narrow v-belts like the 5V series, are measured and labeled by the OUTSIDE circumference.

So, for standard common v-belts you will need to add about an inch or so to your string measurement, again depending on how many pulleys you are going around.

For fractional horsepower and narrow v-belts you will need to add more.  Sometimes a couple of inches.

This page will probably explain things better than I do:

https://hvhindustrial.com/blog/common-types-of-v-belts

Hope that helps clear up some of the confusing aspects of v-belts.  🙂

According to your link it looks like any of the three listed (B, 5V, 5L) would work as long as the length is correct. The belt pictured by Steven above as working on his car is a 5L rather than a B. To my eye the only appreciable difference is the depth and it's only .06" between the B and 5L. With the 5V being the tallest it might grab more of the pulley surface and tend to slip less. Now that my curiosity is aroused I'm going to have to go out to the garage and see what I'm running on my 38. All I told the counter man was a 5/8" belt. I didn't know there were so many options.

@tiny 

The 5L is actually a light duty belt meant for light loads like furnace fans etc normally driven by small fractional horsepower electric motors and without much tension on them.

They will work, but the proper belt for old Chevs really is a B belt.

PS

I learned something on this thread.

I had never thought about early Chevs without generators not having a method of tightening (or loosening) the belt!

With that in mind, a deeper belt with a smaller inner circumference like the 5V MAY be a little harder to roll over the edges of the pulley during installation.

The easiest belt to install (although it will look like an anachronism) might be a notched belt.

I'm not suggesting anyone use one on their old Chevs, just putting it out there.  🙂

PPS

Stephens 5L belt WILL be easier to install due to it's reduced depth compared to a standard B belt.  🙂

When I bought my car in 2003 the belt was very loose and I had an over heating problem, so I tried to get one but no one had a belt to fit. They were either too loose or too short. So I went to an appliance store to get a belt. I told the gentlemen at the counter that it was for a car; he said it wouldn't last. I know on a generator/fan driven car that would be true. However all this runs is a water pump and the engine never gets above 1500 - 1800 RPM's. Much like a washing machine pump motor. It's a good fit. Not too tight and not too loose; that's why it has lasted 21 years. I bought the extra belt expecting it to fail, but it is still going strong.

I have used fractional horsepower belts mostly 5L type for years. Can't recall having one break.

Thanks everyone for their input on this subject. I ended up using a B30 belt and that appears to be working well.