Serpentine Belt Numbers Meaning Explained

[icanfixall]

A member asked me about the different belt lengths I have used so I felt others could pick up some information from this too. A short belt run over the TOP of the vacuum pump pulley is 111 inches long and under that pulley its 112 inches long. Now for the fun part of knowing what the numbers mean on the belts. My Goodyear belt part number is 4061110. I'm no expert but this is what I do know about that number. The 6 tells us the belt has 6 ribs. This is important because there are 6, 7, and 8 rib belts. Only the 6 rib works on our systems. the numbers 111o tells us this belt is 111 inches long. Had it been 111 1/5 inch long the zero would be a 5 for 1/2 inch fraction. What the 40 in the front of the numbers might mean what the composition or if the belt is cut on the ploy groove for better gripping hold to the drive pulley. And by the way the drive comes directly from the crank shaft pulley. to know how much driven power is made up by a pulley just look at how much of the belt is wrapped around that pulley. Also the pulley that needs very little drive pressure will have the belt running on the smooth side of it like is done with the vacuum pump pulley. Feel free to add what you might know about these numbers. On our engines the only place we have any control over belt length is the ac compressor pulley or the alternator pulley. Most of the time the alternator pulley decides what belt we need. My alternator pulley is 2 9/16 inch diameter and my ac comp is 5 inch diameter. The other pulleys can't be changed bigger or smaller. We run what we have.

 

[BDOGONE]

I ran into "short" belt syndrome on my 94 E350. I showed that belt though and crammed it on! Then it showed me and burnt up a " plastic" idler. (NAPA had several listed diameters.) Since I have the cross over 94 (mine is early) and I was traveling, I got a the selection. All well now with a "steel" pulley and 111 1/2" belt.


Sent by wing, prayer & ATT

 

[LCAM-01XA]

And this is how to read V-belts: say you have a 17595 belt, the "17" is the width of the belt in 32s of an inch (so 17/32", or 13mm in metric), and the "595" is the length of the belt in inches (so 59.5", or about 1510mm in metric). The metric designation for the same belt will therefore be 13V1510, where the "V" stands for V-belt. Some manufacturers will write it as 13AV1510, not sure what the "A" there stands for but everything else is the same.

And then we have the NAPA belts, with labels like "259595" - well this particular belt # doesn't seem to exist, you get to choose between #259590 which is 59" long and #259600 which is 60" long - the last three digits show the belt length in inches. The first three digits ("259" in this case) somehow reference both that it's a V-belt and its width, but I'm not sure how and why. Additionally all #259*** belts are listed as 12mm (15/32") wide, while NAPA does list them as direct-fit for IDIs these engines really call for 13mm (17/32") wide belts in all positions except for the short belt between the alt and the vacuum pump. To get the 13mm (17/32") wide belt you need a part #259***HD, where the "HD" part indicates the extra width - those supposedly have different rubber compound also, and are most easily identified by their green in color flat side. Keep in mind that NAPA stores also carry a line of belts called "Power-Fit", those actually do follow standard 17595/13V1510-style designations, but also have the following disclaimer: "Not Recommended For Any Agricultural, Medium Or Heavy Duty Applications". No idea who makes the Power-Fit belts for NAPA, but the #259***-series are made by Gates, with the HD versions probably equal to Gates' own "Green Stripe" line of heavy-duty belts.

 

[Still Strokin]

I'll second all this good info.... We were going thru belt tensioners on here on our 300,000 mile truck like candy... I mean just 2-3 within a couple thousand miles... Ford failed to mention when they redesigned the belt tensioner that they made the pulley larger, thus requiring a 1" larger belt...

 

[icanfixall]

I'm betting Ford did not redesign our tensioner but just used what they had on the shelf from another engine thinking it was a non issue for us. Can you post the diameters of your old and new tensioner pulleys. Also the length of the belt required.

 

[Still Strokin]

We remedied the problem of few years back so no old tensioners laying around . I did measure the current ones though, which is 3 1/4" diameter . Ill look around for the belt part number I used. I just remember the belt ford gave us was so tight the arrow on the damn tensioner wasn't even close to being in between the alignment arrows . Put an inch bigger belt on and it was perfect

 

[Still Strokin]

Here is the part number for the 1" bigger belt...........: RBR K061120,..... came from carquest

 

[whiteboyslo]

Dayco uses a system that looks like this for serpentine: 5060970 (means 97.0" belt, 6 rib. No idea what the '50' means). You might also see them call it a 970K6. Same thing.

That's all I remember from my parts-slinging days.

Mike