Mechanical fan idler pulley replacement - Chevy Impala SS Forum
 
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post #1 of 7 (permalink) Old 02-17-2018, 10:17 AM Thread Starter
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Mechanical fan idler pulley replacement

I can't be the only one to have a bad bearing in the idler for the mechanical fan. Of course, both the idler and the pulley are long since discontinued.

I came up with a solution after a lot of research.

The original 4 groove pulley is 64mm. There are no pulleys made by anyone that are smaller than 70mm. 70 will hit the body of the tensioner.

I bought a 6 groove, 63.5 mm pulley. Gates 38082. Here are the modifications needed to make it work.

The lip on the inside of the pulley (either side, it doesn't matter) needs to be made a bit smaller. I used a grinding wheel gently. See attached photo for size of lip needed.

You also need to shim the pulley so that the belt can ride in proper alignment on the inside 4 ribs. I used 2 5/8" machine bushings that I got from my local hardware store. 1 14 gauge, 1 18 gauge. See photo. Then just bolt it together with the original bolt and washer.

See photos for what you end up with. Works like a champ!
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post #2 of 7 (permalink) Old 02-17-2018, 10:27 AM
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I'm not sure that the LT tensioner and the TBI tensioner bearings are the same. But what I did when mine went out years ago was to get an AC compressor bearing and replace it with that. It all was the same. Worked fine till the day I parked it to start working on it HARD.

Mark: Snowman-33

93 9C1: Work & Cubic Ca$h This started with a new headlight and fender Celeritas In Conficiendo
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post #3 of 7 (permalink) Old 02-17-2018, 08:17 PM
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The more important issue is the spring in the tensioner breaking. You can not replace the spring, and there are no new tensioners available. The bearing in the pulley should be easy to replace. I have replaced a number of bearings to renew other pulleys.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html
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post #4 of 7 (permalink) Old 02-17-2018, 09:52 PM Thread Starter
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Near as I could tell, I could get the bearing, but it's cast into the pulley.
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post #5 of 7 (permalink) Old 02-17-2018, 09:54 PM Thread Starter
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If the spring breaks, guess I'll have to convert to electric then. For now I'm good.
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post #6 of 7 (permalink) Old 02-18-2018, 07:47 AM
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You should be able to use a smooth pulley in the manner of the tensioner pulleys on most other systems. The engine and fan pulleys are both ribbed, and would keep the belt in place.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html
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post #7 of 7 (permalink) Old 02-18-2018, 10:56 AM
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I guess I can understand why you did what you did here.
http://www.rockauto.com/en/moreinfo....sn=555&jsn=555
That is if this is the replacement.

Mark: Snowman-33

93 9C1: Work & Cubic Ca$h This started with a new headlight and fender Celeritas In Conficiendo
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