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I was chatting with JPG about my Mark VII motor belt, and he thinks it COULD be an original belt. It has "501330 DF" written on it.

After working on my SS tonight I thought I'd take a closer look at the Poly V belt too. My Poly V belt has to be an original because it says "Magna American" right on it! It also has a model number on it and it reads "501298 DF". That's very close to the motor belt's part number. This isn't proof that my motor belt is original, but it sure make sense if it is.

When I do a search using my motor belt's part number I find belts that are 31" x 1/2". This could mean that the Mark VII actually uses this size belt. I am going to order one and see how it compares to my current belt. It'll be hard to know for sure one way, or another, because belts get stretched and worn. However, it might give us a good idea if that's the correct size. If it ends up being right us Mark VII owners will be smiling!

I'll give an update once the new belt comes.

I think it merely coincidental that 501330 is a common number.

A simple way to identify the poly-v belt is to count the ribs. s/b 13. The belt should fully cover the idler pulley and the drive sleeve pulley.

FWIW the Parts Manual states 507490 and 507491 for the belts.

You're right, it absolutely could be coincidental. However, it seems awfully coincidental that searching that belt number brings up belts that are that close to what the Mark VII needs.

My Poly V belt does cover the entire pulley, and like I said it says "Magna American" right on it. So, there is no doubt my Poly V belt is original. The fact that their model numbers are so close 501330 DF / 501298 DF makes me think that both are in fact original belts.

That being said, I can't prove the motor belt is original because it doesn't say Magna American on it. However, there are a LOT of coincidences pilling up making it hard to disprove it.

Here are a couple of pics of my poly v belt.

Also, I ordered the motor belt, and it should be here next week. Once it gets here I'll take pictures of both the old belt, and new belt. I'll also measure both belts to see how they compare.


Mark VII Poly V Belt

I took my motor belt off today and measured it. I measured it several times, so I think I have the correct length of my current belt. It measured 29.5" in length, and 1/2" wide. Once I get the new belt I'll see for sure if I measured correctly, or if they are in fact different belts.

IF my motor belt is original we might have been looking for belts that are too long. I ordered a 29.5" x 1/2" belt too, so when that comes I'll see how that compares to my current belt.

OK, as promised I am returning with an update.

Just to recap, my Poly V Belt is an original belt. I am trying to determine if my Motor Belt is original as well. I believe it is. JPG said that the belt should be 1/8" down from the end of the sheaves depending on what speed it is set to (high/low). My belt is exactly that on both high and low speed. Also, the part number for the motor belt ends in "DF", and my original Poly V Belt's part number also ends in "DF". The part numbers themselves are also very close to each other.

Now, the Mark VII parts manual shows a different part number than what is printed on my motor belt. However, I don't believe this proves my belt isn't original. My Poly V Belt is original, and it also has a different part number printed on it than what the manual says. I believe the part numbers were changed in the manual at one point, and this is why it doesn't line up. Just a theory until I can prove it!

So, I ordered two new motor belts.
-First belt is 31" x 1/2" (ordered based on my current belts part#)
-Second belt is 29.5" x 1/2" (ordered based on my measurements of my current belt)

The 31" x 1/2" belt arrived today. It was obviously too long. I ordered it before I measured my current belt, so I was going by part number only. So, that belt is a bust. However, I will say that it did measure a true 1/2" wide just like my current belt. I was worried that it wouldn't be a true 1/2" wide.

My 29.5" x 1/2" belt comes tomorrow, so I am looking forward to checking that one out! Stay tuned for more!

It gonna be short.

You could be absolutely right. If I measured my current belt wrong the replacement belt won't be right. However, if I measured my current belt correctly the replacement belt should fit perfectly. I'll find out tomorrow.

Ok, I got the second belt (29.5"x1/2") today, and it's a perfect match!

I hand cranked it from high-low-high and it was 1/8" from the top of the respective sheaves each time.

For $5 a belt I'll probably be ordering a few just to have them on hand.

Gotta say I'm pretty happy about it!

n240sxle91 wrote:Ok, I got the second belt (29.5"x1/2") today, and it's a perfect match!

I hand cranked it from high-low-high and it was 1/8" from the top of the respective sheaves each time.

For $5 a belt I'll probably be ordering a few just to have them on hand.

Gotta say I'm pretty happy about it!

How you measuring the length?