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Old 08-01-2011, 04:31 PM
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v belt pops off under high rpms

I have a SBC with v belt style front accessories. Whenever I take the engine to 6000rpms or higher the belt that drives the waterpunp and alternator pops off.... any ideas.. pulleys all look pretty damn close
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Old 08-01-2011, 04:39 PM
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I had the same problem on my BBC. I took a lazer light and laid it in the groove and shot it to the other pulleys. It revealed that I was about 1/8" off. I shimmed it out and it fixed the problem. Also, What type of alt bracket do you have. Sometimes they will flex under heavy load and allow the belt to mis-align.
I now have a march bracket and it doesn't move at all. May have to shime the water pump pulley also.

Also, you may want to try a belt that fits totally inside the pulley.

Just a few thoughts.
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Old 08-01-2011, 04:39 PM
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Either they are mis aligned or your getting a lot of belt deflection (whip) and it is slinging the belt as a result.
Small blocks had the smog pump below the alternator , that is where you want to run an Idler, to stop the deflection.
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Old 08-01-2011, 05:05 PM
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I just realized I don't have the bottom bracket in the picture on... Will it make a difference
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Old 08-01-2011, 05:07 PM
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It needs to be on, the alternator is probably flopping around causing the trouble.
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Old 08-01-2011, 05:09 PM
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okay brb ill run out and figure out where it goes.
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Old 08-01-2011, 05:23 PM
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I would say that is def your problem.

I would ditch that one and get one simular to this.

http://www.summitracing.com/parts/SME-2000/
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Old 08-01-2011, 06:12 PM
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Quote:
Originally Posted by NOlowrider
I would say that is def your problem.

I would ditch that one and get one simular to this.

http://www.summitracing.com/parts/SME-2000/
Hmm that looks a lot nicer and isnt priced too bad. Thanks for all your input. Ill take the car out tomorrow and do some pulls and see how the belt holds up. Thank you everyone for the quick responses!
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Old 08-01-2011, 06:34 PM
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No problem. Hope we helped.
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Old 08-01-2011, 08:25 PM
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back in the day

Run a smaller crank pulley so your belt does not go as fast. we used to get corvette pullies. some guys would explode a generator with a good high rpm cam, carb, headers etc. not as much charge at low rpm
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Old 08-01-2011, 09:26 PM
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Quote:
Originally Posted by timothale
Run a smaller crank pulley so your belt does not go as fast. we used to get corvette pullies. some guys would explode a generator with a good high rpm cam, carb, headers etc. not as much charge at low rpm
I wouldn't change to smaller pulleys, that would slow down your water pump, etc. If alignment is good, try deep pulleys.

Explode a generator??? Can you explain? If the system isn't calling for charge, and the regulator is working correctly, why would it be an issue?
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Old 08-02-2011, 06:56 AM
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Originally Posted by 68NovaSS
Explode a generator??? Can you explain? If the system isn't calling for charge, and the regulator is working correctly, why would it be an issue?
Centrifugal force. It doesn't even need to be wired. I've never seen it but I can sure believe the possibility as an alternator has a lot of mass, poorly shaped, and is over driven.
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Old 08-02-2011, 07:11 AM
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cavitation

Hopped up Ford flatheads would cavitate the water pumps at high rpm's create enough vacuum that the water would vaporize , slow down liquid flow. a problem in boat propeller design. In the old days some guys would modify the water pump impellers . My fan belt used to turn upside down, and become round like a rope because of misalignment. generator moved to make room for all those carbs.
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Old 08-02-2011, 07:52 AM
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Quote:
Originally Posted by KMatch
Centrifugal force. It doesn't even need to be wired. I've never seen it but I can sure believe the possibility as an alternator has a lot of mass, poorly shaped, and is over driven.
Maybe if it spun your motor up to 20 or 30,000 rpm's? I've thrown and rolled belts in some of my modified flatties years ago, and on my blower motor, but an alternator "exploding"? Whatever...
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Old 08-02-2011, 08:18 AM
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Quote:
Originally Posted by 68NovaSS
Maybe if it spun your motor up to 20 or 30,000 rpm's? I've thrown and rolled belts in some of my modified flatties years ago, and on my blower motor, but an alternator "exploding"? Whatever...
I would have called anyone a liar telling me a ball joint in an upper control arm in a Durango blew up when cutting out the rivets - had I not been healing from shrapnel in my arm and a bruised gut as I type this. No, it didn't "pop", it blew the hell up leaving me deaf in the left ear for the rest of the day. An alternator blowing up? Not likely, but who am I to call BS?
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