Alternator conversion determining correct belt size

[Jim in LA]

Trying to determine correct belt for my 8N. I have the alternator and mounts positioned where I want them and I took a string and wrapped around the pulleys and come up with 38 inches. That would be the inside dimension of the belt. A Gates TR20412 is the shortest from Gates. I have a TR20451 which is 19/32X45 1/2 and is maybe two inches too long. A B belt is 21/32, roughly 5/8. Any recommendations?

 

[HFJ]

not sure if u have a shorter route than normal, i had no problems finding the length i needed. you definitely want a 5/8" belt, and the pulley to match it on the alternator. i'll have a look at which one i have on mine now. i saved the cardboard for just such an occasion

 

[HFJ]

my current belt is a B42, and i'm happy with the length. long enough to keep the alternator off the manifold, short enough to keep it out of the steering.

 

[jimtrs]

(quoted from post at 09:58:35 09/18/23) Trying to determine correct belt for my 8N. I have the alternator and mounts positioned where I want them and I took a string and wrapped around the pulleys and come up with 38 inches. That would be the inside dimension of the belt. A Gates TR20412 is the shortest from Gates. I have a TR20451 which is 19/32X45 1/2 and is maybe two inches too long. A B belt is 21/32, roughly 5/8. Any recommendations?

38 inches will be too short. Ive done a dozen or more 12 volt conversions on late 8N's, and always end up using a 41 or 42 inch belt. Usually the 41 inch. Try Gates 6941 or 6942.

The goal, obviously is to use the shortest belt possible, to leave room for adjusting. Sometimes this means dismounting the alternator to install the belt.

 

[Jim in LA]

Gates TR20412. 19/32 X 41 1/2 I have one ordered, it will be at parts house in the morning.
They let me test a 38 B belt and It was way too short. I figured a 41 or 42 should be ok. PPO
had a narrow, maybe 3/8 belt on it that slipped way down in the pulley plus it had numerous
cracks in it.

 

[HFJ]

(quoted from post at 10:58:35 09/18/23) Trying to determine correct belt for my 8N. I have the alternator and mounts positioned where I want them and I took a string and wrapped around the pulleys and come up with 38 inches. That would be the inside dimension of the belt. A Gates TR20412 is the shortest from Gates. I have a TR20451 which is 19/32X45 1/2 and is maybe two inches too long. A B belt is 21/32, roughly 5/8. Any recommendations?

sorry, forgot to ask - front or sidemount? my B42 is on a frontmount.

 

[Ultradog MN]

Buy it locally.
Buy 2 or 3 different lengths.
Tell them you will eturn the ones you can't use.

 

[DennyD]

And it's important to make sure you have the belt correctly aligned with the alternator. Something as simple as the placement of the washers with the mounting hardware can offset the alternator from the pulley, so go slow and pay attention if you happen to take the alternator off entirely to install the belt, once you think you have a belt of the correct length.

 

[Jim in LA]

Update: Gates TR20246 belt fit. Alternator alignment looks good now.

 

[DennyD]

Actually, the belt on my 8N is 45" long, a Gates PowerRAted 6945 (#5l450K, with a thickness measurement of 21/32" on the label).

 

[Tall T]

(quoted from post at 06:58:35 09/18/23) Trying to determine correct belt for my 8N. I have the alternator and mounts positioned where I want them and I took a string and wrapped around the pulleys and come up with 38 inches. That would be the inside dimension of the belt. A Gates TR20412 is the shortest from Gates. I have a TR20451 which is 19/32X45 1/2 and is maybe two inches too long. A B belt is 21/32, roughly 5/8. Any recommendations?

Something to watch for:
I ordered a water pump assuming it was the correct pump because they said it had a 3/8" pulley. My belt is the narrow one (3/8 ). So I get the pump all the way from back east and the cast pulley they sent took a 5/8 wide belt!

They actually used the width AT THE BOTTOM OF THE GROOVE which is 3/8", and called it a 3/8" pulley.

So I got on their case, got a total refund and they paid for the shipping back to them because I told them they had misrepresented the pulley and belt size on their web site.

I showed them the web page at Chev's of the 40's representing the pump and pulley correctly. I got the correct pump from Chev's and it turned out to be a perfect beauty, made in japan.

T

This post was edited by Tall T on 09/23/2023 at 12:00 pm.