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Old 05-28-2014, 02:13 PM   #1
Larsonlegacy
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Question squeals and pulleys

Greetings,
This is my first thread on this forum, and I hope to be able to contribute more in the future. I have a 1968 GMC C2500 with a 396. The truck was purchased by my grandfather new in 68 and has been passed along so I know quite a bit of the history.
I finished a full rebuild of the engine this month. (bored to ~ 402, new everything including alt, water pump, harmonic balancer) i was hoping that the engine squeal that it has had since I was a child would be remedied with the rebuild..., no such luck.
I have read several threads on squeals and pulleys but I think my situation calls for a little more info. The squeal happens around 2500 rpm whether its under load or just revving and continues until rpms drop. I know its the crank/wp/alt belt. It is also damaging the belt on both sides (not top and bottom). Diameter of crank: 7.8" lwp: 6" alt:2.7" interesting thing is the part number stamp on the WP pulley pulls up a '72 corvette with 350? So I am sure that pulley is wrong. My father remembers something about having the crank pulley replaced for some reason, but cant remember details. Does anyone know the original sizes of the pulleys that this truck came with? The pulleys are lined up as best I can tell. I have no idea where to start and funds have been almost depleted by this point. So I can't throw pulleys at it blindly.

Thanks!
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Old 05-28-2014, 02:34 PM   #2
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Re: squeals and pulleys

Since the pulley grips the belt by the tapered sides I would make sure one of the pulleys doesn't allow the belt to touch the bottom. That's the only thing I can imagine would cause a problem for that long. Just see if the belt sits the same depth in each pulley. If it's in one further then the others it's probably your culprit.
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Old 05-28-2014, 04:47 PM   #3
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Re: squeals and pulleys

Thanks for the direction on that. I had read about the Vbelts NOT sitting low enough, which I though might be the crank pulley, but looking at it now, the belt sits below the top of the groove on the wp pulley. Which would makes sense with the destruction of the sides of the belt. Thank you, I think I am convinced its the wp pulley.
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Old 05-28-2014, 05:20 PM   #4
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Re: squeals and pulleys

have you tried leaning on it and tightened the crap out of the belts?? many times that is all that is required especially on the power steering belt
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Old 05-28-2014, 05:32 PM   #5
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Re: squeals and pulleys

What kind of belt are you using? I had the same problem with my 454 and on the 4.3 in my blazer. Kept getting cheap made belts from autozone/OREILLYs, and finally went back to the Goodyear gator back belt. As soon as I put the belts on, no more squeaking. I hope it's as simple for you.
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Old 05-28-2014, 09:57 PM   #6
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Re: squeals and pulleys

Aerosol belt dressing does a good job eliminating squeals, but sounds like you have a worn pulley you already identified. Wouldn't recommend the "lean into it" option for anyone as that will put too much radial load into the bearings...if there is a noise in a belt system there is a fix for it that doesn't involve over tightening; in general you should be able to get 1.5 times the cross-section thickness of the belt in deflection
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Old 05-29-2014, 03:38 AM   #7
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Re: squeals and pulleys

I have tried several belts from Oreille's, Napa and one from amazon.. Not sure about the brand names, however. There was no difference between the belts, but I guess it would hurt to try something a little more reputable. And the belt dressing had no effect either.
I also did over tighten the belt to see if it helped at all, but again, no dice. It did change the pitch of the squeal though.. Lol
I ordered a new WP pulley from Jegs and will update when it arrives. The only other concern I have regarding all of this is that I have less than 1/8 inch play in the alternator position. (between the valve cover and alt when belt is tight) Meaning that I have to remove the alternator to remove the belt. This doesn't seem right, but all parts stores give me the same length belt.
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Old 05-29-2014, 09:07 AM   #8
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Re: squeals and pulleys

Quote:
Originally Posted by Larsonlegacy View Post
The only other concern I have regarding all of this is that I have less than 1/8 inch play in the alternator position. (between the valve cover and alt when belt is tight) Meaning that I have to remove the alternator to remove the belt. This doesn't seem right, but all parts stores give me the same length belt.
Usually the length of the belt is in the part number. Assuming changing the length of the belt won't make it rub against anything else, have them give you a couple sizes longer or shorter and see if that helps with clearance. I will warn against just going into Autozone and giving them a length, for some reason Autozone workers tend to not be able to think outside of their computers (just my experience).
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Old 05-29-2014, 10:04 AM   #9
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Re: squeals and pulleys

Quote:
Originally Posted by Larsonlegacy View Post
I have tried several belts from Oreille's, Napa and one from amazon.. Not sure about the brand names, however. There was no difference between the belts, but I guess it would hurt to try something a little more reputable....
O'Rileys has a house brand which is no good; they also carry Gates which is very good. Same for Advance I believe. NAPA also has Gates as does CarQuest. AutoZone has a cheap house brand and has GoodYear which is fine. Always buy the better belts IMHO (same thing with hoses too). I use Gates on everything.
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Old 05-30-2014, 12:51 AM   #10
Larsonlegacy
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Re: squeals and pulleys

Thanks for the info on belts, I plan on trying a gator back belt after trying the pulley. I'd rather have a solid answer to the cause.
I hear ya on the Autozone thing.. . I don't really go there for advice. I will be sure to update this thread when I have an answer!
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Old 06-11-2014, 02:32 PM   #11
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Re: squeals and pulleys

*UPDATE* I replaced the wp pulley (significantly different from old one) and it changed the squeal in pitch and rpm. I also used the gator belts as suggested with no difference. I have now ordered the crank pulley which also looks significantly different from what's on there now. I guess I should have just gone with a full pulley kit. Oh well... Update in a week or so when the pulley comes in.
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Old 08-07-2014, 11:13 AM   #12
Larsonlegacy
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Re: squeals and pulleys

*SOLVE D* I realize this update is really delayed, I got married and moved on out to Portland which takes some time... Anyway, after replacing all the pulleys and still having squeals, I started replacing mounting brackets. The ALT bracket was the one that fixed it! It seriously did not look misaligned but I'm squeal free. THANKS for all the feedback and help!
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