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08-22-2019, 10:23 AM | #1 |
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Join Date: Mar 2016
Location: LaGrande Oregon
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Rule of thumb for fan belt tightness
Is there a rule of thumb that you guys use for belt tightness? This is for my avatar 302 engine. Thanks!!
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08-22-2019, 12:38 PM | #2 |
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Location: Wilmington, NC
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Re: Rule of thumb for fan belt tightness
I've used one inch. Seems to work for me.
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08-22-2019, 12:38 PM | #3 |
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Re: Rule of thumb for fan belt tightness
Thank you 56!
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08-22-2019, 02:05 PM | #4 |
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Re: Rule of thumb for fan belt tightness
I go with trying to spin the alternator pulley by hand. If I can't, it is tight enough. The # of deflection depends on how long that section of belt might be.
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08-22-2019, 02:34 PM | #5 |
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Re: Rule of thumb for fan belt tightness
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08-24-2019, 01:56 PM | #6 |
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Re: Rule of thumb for fan belt tightness
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08-24-2019, 08:08 PM | #7 |
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Re: Rule of thumb for fan belt tightness
What started this thread is that the bolt that goes thru the alt housing sheared off flush with the head. Sometimes the belt would squeal before this happened. It is a 7/16" by 6" bolt. This allowed the belt to slip significantly so both the alt and water pump stopped working. I lucked out by being able to unscrew the bolt out of the head with my fingers so I think that this bolt was loose. I put in a new grade 5 bolt. I tightened the tension so there is no squeal but the belt is quite tight-maybe a half inch on the longest travel. Is this too tight? Comments please.................
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08-24-2019, 08:22 PM | #8 |
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Re: Rule of thumb for fan belt tightness
A lot depends on the accessory being turned. On my 272 the AC compressor is turned by the water pump belt. It is not the best situation in my opinion because it has to be pretty tight to run the compressor and I'm concerned about the water pump bearings.
As long as the driven accessory doesn't squeal I would think it is tight enough. The belt can get slick and hardened on the "V" and cause squealing. Check for that. I had a 5.0 with serpentine belt that was tensioned by a factory tensioner. That joker was tight! I suppose the components were built for it. |
08-24-2019, 09:35 PM | #9 | |
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Re: Rule of thumb for fan belt tightness
Quote:
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08-25-2019, 06:43 AM | #10 |
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Location: Marana Arizona
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Re: Rule of thumb for fan belt tightness
Not a fix, but a band-aid is to take a bar of soap and carefully touch it to the contact side of the belt while the engine is running. Works to stop the squeal if your on the road. If the belt is still pliable with no cracks it almost has to be a matter of finding the "sweet spot" in the adjustment. I have has a new belt that just wanted to squeal and when replaced with a old used spare I had, the squeal ceased...
I wonder why belt pulleys are smooth and not knurled to better grip a belt? Chap |
08-25-2019, 10:39 AM | #11 |
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Re: Rule of thumb for fan belt tightness
an alternator needs to be tight or it will slip.they are short so the bearings will take a lot more than a generator.you can overdo it and damage the front main bearing but that would take a lot.
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08-25-2019, 11:08 AM | #12 |
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Re: Rule of thumb for fan belt tightness
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08-25-2019, 11:08 AM | #13 |
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Re: Rule of thumb for fan belt tightness
Thanks darrell and chap. I will work on finding the sweet spot some more. Thanks all for the help!!!!
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08-25-2019, 11:26 AM | #14 |
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Re: Rule of thumb for fan belt tightness
Universal Belt Tension Gauge - OTC 6673 Don't forget proper belt application/sizing, quality of belt and possible glazed pulleys.
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08-25-2019, 02:02 PM | #15 |
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Re: Rule of thumb for fan belt tightness
Thanks for the belt tension gauge pic, Kultulz. I've been meaning to get one of those, but didn't know what they looked like.
I've used 3/4" total lateral play slack as a standard on my '54. When my car encountered minor charging issues recently, the belt had loosened to 1-1/4" total lateral play. I didn't think that would be enough to make a difference, but when I tightened back up to 3/4" it made a measurable difference in charging. That wasn't the only issue I was facing, but it did help. |
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