need some belt help

1bad67sbf · May 19, 2011

i have stock pulleys and no ac (frpp delete) or smog. i came up with needing a 73in belt but carquest got me a "73.0" belt but it was to short. i want to know what belt part number people run with my set up. thanks

LX302 · May 20, 2011

So you calculated you needed 73" and got a 73" belt and it was too short.
Hmm, sounds like your calculation is off.
How did you calculate the length?
I always recommend using a length of string routed the same way the belt would go around the pulleys to get close to the size you need. Measure the string after you wrapped it around the pulleys and get a couple belts within 5mms of each other so you don't have to keep running back to the store.

giddyup306 · May 20, 2011

LX302 said:
So you calculated you needed 73" and got a 73" belt and it was too short.
Hmm, sounds like your calculation is off.
How did you calculate the length?
I always recommend using a length of string routed the same way the belt would go around the pulleys to get close to the size you need. Measure the string after you wrapped it around the pulleys and get a couple belts within 5mms of each other so you don't have to keep running back to the store.

I used to do this when people were too cheap to fix things like air compressors... I measured it with a string just like you do. Then I go to the parts store and get three belts. One of the exact measurement, and one bigger, the other smaller. Then I take two of them back. Once you know the width of the belt you can look up the same style on the first part of the part number. The end is the length in millimeters.

90lxcoupe · May 20, 2011

different belts from different companies will vary in size. The last time i measured for a belt i used a piece of nylon line from a weed trimmer spool and got the measurement on the money the first time. I think this may work better than the string because there is no stretch to it. Also, keep the line on the same rib when you are running it on the pulleys. This will get you a consistnet size.

Then use a credit card and buy like 5 belts. Thats how i usually do it, 99% of the time you are off by a belt size or two. I get the belt i think it is, then 2 sizes smaller, 2 sizes bigger

tims 86 · May 20, 2011

took me three trips to get the correct one.. tried the string method, didnt work for me. i think i ended up with a 68.5

1bad67sbf · May 20, 2011

yeah i started with the string but it did not work because i got a 68in belt and it was way to short. i got the 73 from this graph but it was to short and a 73 1/4 was to long so i thought is someone had this setup they may know what the part number was

giddyup306 · May 20, 2011

1bad67sbf said:
i got the 73 from this graph but it was to short and a 73 1/4 was to long so i thought is someone had this

I don't know what you're doing wrong, but there is no way that a 73" can be too short and a 73.25" be too long. Your tensioner will move several inches.

Make sure you are routing the belt correctly. Use the diagrams that you posted if you need to.

1bad67sbf · May 20, 2011

i feel the same way but the 73.25 slightly touches itself at the tensioner. i asked the parts store guy how the hell could a 1/4 in change go from too big to too small and his answer was to try to get a part number and try that. the 73 was a double side 6 groove belt but it did say 73 in. i dont know i just want a damn belt on the motor.lol

giddyup306 · May 20, 2011

1bad67sbf said:
i feel the same way but the 73.25 slightly touches itself at the tensioner. i asked the parts store guy how the hell could a 1/4 in change go from too big to too small and his answer was to try to get a part number and try that. the 73 was a double side 6 groove belt but it did say 73 in. i dont know i just want a damn belt on the motor.lol

Then take a picture, and maybe we can see what is going on. Also did you physically measure the belt? There is a chance that it might have been mislabled or mispackaged.

1bad67sbf · May 20, 2011

i should have checked the belt but i was fed up and just returned all of them, i will try another autoparts store like autozone or napa. i just wish i could say what car has this size belt or what a goodyear or dayco part number is.

sleekkat232 · May 20, 2011

for stock pulleys on a fox 5L with the smog pump deleted (not around the pulley at all, not just the delete bracket) uses an 87" belt... i have underdrives on mine and i use an 83.5" belt
i dont know how you guys are using sub-80" belts...
please elaborate...

giddyup306 · May 21, 2011

sleekkat232 said:
for stock pulleys on a fox 5L with the smog pump deleted (not around the pulley at all, not just the delete bracket) uses an 87" belt... i have underdrives on mine and i use an 83.5" belt
i dont know how you guys are using sub-80" belts...
please elaborate...

The last picture in post #6...

Mustang5L5 · May 21, 2011

1bad67sbf said:
yeah i started with the string but it did not work because i got a 68in belt and it was way to short. i got the 73 from this graph but it was to short and a 73 1/4 was to long so i thought is someone had this setup they may know what the part number was

I don't like the bottom left picture here because it doesn't give much wiggle room for the belt and tensioner to not rub on each other.

I am using the top right method with bypassed smog and ford racing delete. Even though it says in the photo the belt wraps around the a/c pump, it works because the ford racing delete puts the p/s up in the same spot.

This method gives you plenty of room under the tensoner so it doesn't hit, and allows more belt sizes to fit.

No idea what I'm running though as I have custom size pulleys and its been years since I put this belt on.

IMHO...do not use the bottom left method

1bad67sbf · May 21, 2011

thanks mike i will try that. i just wish i had tried when i had the belts in hand. my luck i returned a belt that would have fit with that setup.

85_SS_302_Coupe · May 21, 2011

If you do a search for threads i have made, i made one talking about how basically you can gain or lose as much as an inch in belt length just by loosening the power steering and alternator bolts and wiggling the brackets around. There is enough play in those bolts holes to allow a lot of variance in belt length. If you're almost there with a certain belt length, loosen everything up and see if you can pop the belt on, then tighten everything down. By the time you need to take the belt off again, it will have stretched enough to allow it to go on easy the next time.

Trust me on this, been there and done it 100s of times...it's quite frustrating but this one detail made all the difference in the world.

1bad67sbf · May 21, 2011

thanks

tims 86 · May 22, 2011

i used the bottom left one with no problem,, just a really short belt and the underdrives make it shorter. 68.5

1bad67sbf · May 24, 2011

thanks mike, that + a 75 inch belt got me going

LXFIVEOYEAH · Jul 28, 2011

top right pic works awesome with the ford racing ac delete bracket 70in. belt with ander drive pullyes on crank only

mustanglx91 · Jul 28, 2011

I always have a set up like the bottom left. Think I used a 76.5 belt with stock pullies with no issues.

need some belt help

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