Underdrive pulley belt clearance


New Member
Apr 29, 2004
Ok I installed a set of ASP Aluminum UD Pulleys removed smog and routed belt like this pic below. I ended up with a 89.5” belt fit nicely but the clearance between the water pump pulley and the idler pulley is very tight I’m talking 1/8 to 1/16 of inch with belt on. Is that normal? :shrug: Also when start I think the belts rub for a second because it squeals, but after start there is no noise.

Modified pic from Stangfreak95 thanks.


Edit:fix pic
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I actually used the same size belt...

It seemed tight at first but it will loosen a little bit.

I don't know about the rubbing though.. :shrug: If it's just when it starts maybe it quickly loosens a bit so it doesn't squeal...

They do make a 89.7 belt though, you may want to check that out..
I used the same belt with my pullies. As long as you have clearance, you are fine. The belt will be a bit tight till it stretches. On my car, the tensioner clattered, because it was hitting the stop. I had to use the dremel to grind back the stop a little to stop the clatter.

You guys are wrong. The reason a belt squeals at first is becaust it is TOO LOOSE. Therefore it slips (causing the noise). When the belt heats up, it grabs better and squeals less. If the A/C compressor is on, it will squeal even more, since there is strain.

You have to look at the pulley tensioner notch and see where it lines up. That will tell you if it is too loose or tight.