Engine 1987 belt size

R82148V

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May 26, 2020
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Hello Everyone,

I have a 1987 vert, manual, 5.0, factory ac, smog.. Everything from the factory is still there. I’m having such a hard time figuring out the belt size. Everything I look up says 92 3/8” for a 87 manual with ac. I did the rope measure trick while pulling the tensioner to the middle of the gauge and it measured a little under 90”!
I’m completely confused. all pulleys are stock too. nothing deleted.

Thanks for all your help!!!
 
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Wayne Waldrep

Before I post a pic, do you have one of yours?
15 Year Member
Apr 14, 2003
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The reason I ask is this. It was typical for me over the years to change stuff around on my car. Many times I'd drive the car to the parts store and grab a handful of belts and see which one fit best. This required me to get there though. Why I would change it after driving there I can't remember...lol.
But I've done it numerous times. You just guess at first and get close then fine tune. Do not buy a belt that is close to max length because it will stretch and bottom out your idler. I like to buy one that I can barely get under the idler and let it stretch. If you have to drive something else to the parts place them just get the closest one to your string measurement and make sure you can return it for a swap. If they won't, go to a place that will.
 
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Mustang5L5

Put lubricant all over the balls
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Did you try the belt? If everything is stock, then the stock belt should fit.

the rope trick gets you in the ballpark. It will always be 1-2” off in either direction which is why people say to buy the belt in the lenght you measure and then one size up and down. Return the two that don’t fit.

install a belt that is a little on the tighter side. After a few thousand miles it tends to stretch a tiny bit so the tensioner will relax
 
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R82148V

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May 26, 2020
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So do you not have even an old belt laying around?
I actually do have the old belt and can see the part# on it.. It comes up as 90".
LMR.com states this size will only fit on 1987 automatic and 1988 - 93. I did have all the accessories, pullies and brackets off for inspection, cleaning and painting. I wonder if when installing everything, it changed the overall belt size by each accessory moving over ever so slightly when tightening.

In any case, I'll do what you guys are saying, get a few belts and use the only thats a little tighter to allow stretch room.

I'll let you know what happens!

Thanks again!
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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The alternator was different for the 1987 manual trans cars. It was 65amp. The 1987 AOD and all 1988 and later had a different alternator at 75 amps. However, in the 30 years since 1987, most parts stores and Ford have replaced that smaller alt with the 1988 version.
 

R82148V

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May 26, 2020
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UPDATE - I picked up a 90" belt for 1988 and up. It went right on putting the gauge a little before the halfway mark.

Thanks again!
 
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