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Cure for Tossing Fan Belts?
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DRR Sportsman
Picture of FootbrakeJim
posted
My son's BBC Chevelle has developed a habit of tossing the v-belt when he spins it over 6,000 RPM. It is a very basic, stock-style setup circa 1970 - Non-A/C car, has only 2 belts, P/S pump belt stays put just fine, but the Alt/Water Pump belt is the one that he keeps losing when he revs it past 6K. (Normally shifts it at 5800 and belt stays on). He says he has tried running it loose, tight, very tight, no matter. Crank pulley is aftermarket aluminum billet. Stock Water Pump pulley. Alternator has a larger diameter (5"?) Moroso deep groove aluminum pulley on it. I went over and eyeballed it, pulled out a long straightedge, and everything seems to be lined up perfectly, along all 3 "sides" of the belt "triangle". Had him run it, and didn't see any runout or wobble on any of the 3 pulleys. I jokingly told him "just keep it below 5800", which he did not find humorous. Roll Eyes
Car never had this problem before, could it be a sign of other troubles? (Damper, crankshaft, bearings in pump or alt, etc)? He said it ruins the belt whenever it gets tossed, they get a permanent kink or bend in them, won't stay on at all after that. Also said he has tried 3 different brands, and even going to a 1.5" shorter length to bring the pulleys closer together.
I don't know what else to advise him, other than put an electric water pump on it...
I still have most all the same parts from my old setup, which I spun to 6800 thousands of times, I guess we could swap things out and see if it cures the issue. What would you change out first? Alt, Bracket, pump pulley, crank pulley, then pump? (Order of easiest to hardest), Or swap out everything all at once?
(Or - ?) Confused

Thanks in advance.

This message has been edited. Last edited by: FootbrakeJim,


Dan "Jim" Moore
Much too young to feel this damn old!!
 
Posts: 1059 | Location: Farmersville, TX  | Registered: December 05, 2002Reply With QuoteReport This Post
DRR S/Pro
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Pulley alignment, belt to wide for pulley, alt. mounting brackets not strong enough, non deep grove pulleys are all causes! Also use a smooth belt in the inside of it, no steps.
 
Posts: 2161 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR S/Pro
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Years ago NAPA had a premium, I'm thinking deep groove, V-belt you might explore.


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Posts: 2350 | Location: OKC, OK | Registered: February 15, 2008Reply With QuoteReport This Post
DRR Trophy
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I suggest a narrower belt so it fits inside the pulleys ,that's the route I took never lost a belt
 
Posts: 65 | Location: central indiana | Registered: May 16, 2016Reply With QuoteReport This Post
DRR Sportsman
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Start changing parts one at a time. Start with the oldest first.
 
Posts: 528 | Location: Southeast | Registered: March 14, 2009Reply With QuoteReport This Post
DRR Sportsman
Picture of 23taltered
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Something is ****ed a little. I'd put your old brackets on it and check for cracked/bent brackets.


Bill Huntington
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Posts: 163 | Location: Northern Cal | Registered: January 06, 2000Reply With QuoteReport This Post
DRR Pro
Picture of AlkyIROC
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Mount a camera under the hood to watch the belt and see why/when the belt gets tossed.

My bracketry is all home made. I spin the engine to 7600 and have never lost a v-belt. I also used a straight edge to make sure all the pulleys were square while I was fabricating.


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Posts: 1355 | Location: Calgary | Registered: June 06, 2001Reply With QuoteReport This Post



DRR Sportsman
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Try a Top Cog Belt. Frequently solves the problem.
 
Posts: 606 | Location: Lakewood, Co. | Registered: January 22, 2007Reply With QuoteReport This Post
DRR Pro
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It throws belts with the Moroso alternator pulley installed?! Jeez! I would suggest not tightening the belt quite so tight, that might help (oddly enough). I also agree with trying to find a premium quality belt. Once you find one that stays put, buy at least two more of them. Seems like whenever I find one that works, they discontinue it. Take care. Tom Worthington


If it seems that bracket racing has gotten too expensive for you, maybe you are just doing it wrong.
 
Posts: 1254 | Location: Rocky Mount, NC | Registered: December 01, 1999Reply With QuoteReport This Post
DRR Sportsman
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Went thru this on my small block camaro. I got rid of the aluminum crank pulley and went back to the stock steel one. I used the largest moroso alternator pulley a narrow belt to ride lower in the pulley groove. Then still had to reinforce the alternator brackets because ultimately that was what was flexing ever so slightly, but enough to toss the belt. Like his one time and belt was done.
 
Posts: 510 | Location: Going to or returning from the chipmine. | Registered: July 01, 2011Reply With QuoteReport This Post
DRR Pro
Picture of Bruce Williams
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quote:
Originally posted by SS427IMP:
Try a Top Cog Belt. Frequently solves the problem.

Top cog belt solved tossing the belt on my wifes Nova.


Bruce Lee Cool

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Posts: 2042 | Location: Chandler Arizona | Registered: August 11, 2005Reply With QuoteReport This Post
DRR Trophy
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Had a similar problem years ago. BB Mopar stuff. Stock brackets made for a long belt. I noticed the belt had a lot of bounce to it going from wide open to off throttle. Also, the bracket moved/bent very slightly as the rpm went up, I assume as engine speed increases, so does stress on the alternator/bracket assembly. Top Cog belts were better, but still came off on occasion. Ultimately, I made up my own bracketry to shorten belt and make a more stable assembly. No more problems after that.

I'm curious if you could find a place to put a tensioner on it. May allow for less belt movement and keep better contact on pulleys.


William Kilduff
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Posts: 120 | Location: Wilmington NC | Registered: June 15, 2014Reply With QuoteReport This Post
DRR Pro
Picture of chasracer
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This is a really old trick but it normally works. You will need a long bolt and matching nut, you might also have to fab a bracket but I doubt it. Somewhere along the longest span of the belt, see if you can get the long bolt into an accessory hole near the belt. The side of the bolt will be contacting the belt during operation and the nut is to tighten the bolt in place as a locknut. It doesn't have to be touching the belt when idling but it should be within an inch of it. As the engine and belt spins up RPM, the belt will flex and move outward, the long bolt will keep it from going to far and coming off the pulleys. I used to run this setup in our '55 Chevy S/S and my '66 Chevy bracket car. Never lost a belt after putting the bolt in place.


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Posts: 1135 | Location: The problem is not the problem. The problem is your attitude about the problem. Savvy?” ~~ Captain Jack Sparrow ~~ | Registered: August 21, 2000Reply With QuoteReport This Post
DRR Pro
Picture of Mike Beck
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If you're tossing the belt with a deep Moroso pulley you have something flexing. How far is that belt sitting down inside the Moroso pulley?
 
Posts: 1444 | Location: South River, NJ | Registered: June 19, 2007Reply With QuoteReport This Post



DRR Sportsman
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quote:
Originally posted by Bruce Williams:
quote:
Originally posted by SS427IMP:
Try a Top Cog Belt. Frequently solves the problem.

Top cog belt solved tossing the belt on my wifes Nova.

I decided to change the 10 year old top cog belt on my Vega. I put a (different brand) belt on it. It threw the new belt off on the first run. I put the old Dayco belt back on. It was still on several years later when I sold the car.


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Posts: 225 | Location: Usually home | Registered: January 27, 2013Reply With QuoteReport This Post
DRR Trophy
Picture of Bad Nusz
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quote:
Originally posted by SS427IMP:
Try a Top Cog Belt. Frequently solves the problem.


The Top Cog belt helped me too. I had such a problem for awhile there I actually bent a piece of flat aluminum strap into a hook and mounted it to catch the belt if/when it flew off.
 
Posts: 377 | Location: Sioux Falls, SD | Registered: March 17, 2018Reply With QuoteReport This Post
DRR S/Pro
Picture of banjo
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I had the same problem a while back. When I switch to a cog belt, it would break the case of the alternator.

Does the alternator bracket use two long water pump bolts to mount?

I finally figured out that those bolts were flexing, so I made a bracket that allowed me to bolt that the alternator directly to the water pump. Further, I added a tab to the spacer that goes between the alternator and the head to bolt to the back of the alternator. Haven't had any issues since.

I would bet your setup is flexing, can you post some pictures of what your working with?


Bill Simpkins
74 Nova
SBC 406
3240 pounds
Speierracing heads

60 1.27 (10/16)
1/8 6.03@111 (10/16)
Best 9.87@131 on the rev limitor 1 Feb 2013


nova

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Posts: 1830 | Location: San Angelo | Registered: March 07, 2005Reply With QuoteReport This Post
DRR Pro
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The threaded rod I used for the pump standoff is grade 5.

 
Posts: 2551 | Location: 53056 | Registered: December 30, 2009Reply With QuoteReport This Post
DRR S/Pro
Picture of banjo
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Did you add that 4th bolt in there? I think that helps.

The problem with the standouts is that when a long bolt gets hot, it expands more than a shorter bolt and it loosens. This is the same reason why many don't recommend the drive mandrals with the long bolts.

So when it gets hot, the bolts loosen a bit and allow things to rock back and forth. It would flex enough to allow the belt to come off.

Mine would also break those bolts. Bolts provide a clamping for and are not ment to take side to side forces. Just like your wheel studs. What happens when your lugs aren't tight enough, the studs flex back and forth until they break. . If using the long bolts, you need a bracket that mitigates the side to side forces on the bolts. The longer the standout, the force has more leverage to work the bolt back and forth.


Bill Simpkins
74 Nova
SBC 406
3240 pounds
Speierracing heads

60 1.27 (10/16)
1/8 6.03@111 (10/16)
Best 9.87@131 on the rev limitor 1 Feb 2013


nova

quarterpanelview

wheelie

FTI Converter
www.speierracingheads.com

 
Posts: 1830 | Location: San Angelo | Registered: March 07, 2005Reply With QuoteReport This Post
DRR Top Comp
Picture of Curly1
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Mine started tossing belt recently. I think the bracket may have bent a little or something but it was not perfectly straight. I put one thin washer between one of the brackets to fine tune it and make it perfectly straight. Problem resolved.


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