hey guys, i need help finding a belt diagram and sizes for an alternator belt for my 86 351w f150. it sheared the old belt and the local parts store swears their system is right but the belt they gave me is about a foot too short. it wont clear the waterpump even. this truck has to be ready and in tip top shape to drive from phoenix to kansas city in a month!!!!

any help is greatly appreciated


THANKS!

 

Anything we can reference will probably be the same as what they have. You must have something that is not stock. What I usually do is hunt up a old belt(I have a few laying around) that is too long, cut it in two, and wrap it around the pulleys like I want it to go, bring it around and mark it. Make sure your tension adjuster is almost all the way to the short side of adjustment. Take the belt off and measure the backbone for length.

When you go to the store, this is how the numbers go; You will have a 13 series belt(13mm wide) and a 15 series belt(15mm wide). You can judge how the belt sat in the pulleys as to what size belt you need. And your measurement belt you used should be the size you want to use to get a accurate length(forgot to mention that in the previous paragraph).

This is how the belt numbers go; Say you need the larger belt, and you need it 45 1/2 inches long. That belt number will be a 15455 or a 45515 depending on what store and what brand of belt you are buying. Some brands reverse the numbers. The 15 is for the 15mm width, and the 455 is 45.5 inches long. If you find you are close, but it's a little bit too long, take the other belt back and get a 15450 (45015) belt. That will be a 15mm width belt that is 45 inches long.

Say you need the smaller 13mm belt, and it needs to be 23 1/2 inches long. That belt number will be a 13235 (or a 23513) belt. 13 mm wide and the 235 is 23.5 inches long.

Pretty simple once you get the hang of it. That way you can take your best guess, and if you need it longer or shorter, you know what belt to get.

 

If you dont have a belt, use a piece of clothsline rope for Dave's method. cut the rope to length so it will be taught, then measure it