Drive belt wobble



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vanguy16
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Drive belt wobble

Post by vanguy16 »

Does anyone else see significant belt wobble on their 318's? I'm seeing a significant wobble l from the alternator to crankshaft span.
Just wondering if it's normal because it's quite a long run.
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Faulkner
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Re: Drive belt wobble

Post by Faulkner »

Loretta has an alternator, Mike? Not a generator?

Any chance you can take a video, and post it here? Perhaps then we can advise.
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vanguy16
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Re: Drive belt wobble

Post by vanguy16 »

Hi Dan.

Yes, it's been upgraded to an alternator. Unfortunately I've taken video but the vibration doesn't show on video well at all.
vanguy16
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Re: Drive belt wobble

Post by vanguy16 »

Imagine that wobble being 20-30 times faster as the camera smooths it out so to speak.
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Faulkner
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Re: Drive belt wobble

Post by Faulkner »

Ah, I didn't read correctly; I thought at first perhaps a pulley was wobbling. That doesn't seem to be the case.

The crankshaft pulley is providing the pull on the belt, first the water pump & fan pulley, then the alternator pulley. Any slack in the belt will appear between the alternator and the crank pulley. Are you sure the belt is good and tight? I'll ask Dick Koch to review this thread and comment as well.

Dan
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Mark Merritt
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Re: Drive belt wobble

Post by Mark Merritt »

Looks like there is slack on the bottom side, motor turns clockwise. Does the alternator bearing spin free when off the belt? Mark
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Dick Koch
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Re: Drive belt wobble

Post by Dick Koch »

Single groove pully on crankshaft. I guess no power steering. The belt is tightened correctly when you push down in the middle of a span and it moves approx. 1/2". Dan can you post the video of my engine running while driving the alternator, AC compressor and water pump.
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Faulkner
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Re: Drive belt wobble

Post by Faulkner »

Sure, Dick - Mike, here's a vid of Dick's 318 running. You'll note that there isn't any play in his fan belt. Check the tightness of the belt, and failing that, confirm that the alternator isn't hanging up, as Mark suggested by removing the belt and checking the free play.

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vanguy16
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Re: Drive belt wobble

Post by vanguy16 »

Man that is a nice looking 318.

I will check tightness. I don't like the fact the alternators on a large arm that I think might even have some give when you really tighten the belt. I will also check the alternator pulley.

Thanks guys.
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Faulkner
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Re: Drive belt wobble

Post by Faulkner »

vanguy16 wrote: Sat Jun 18, 2022 6:52 pmI don't like the fact the alternators on a large arm that I think might even have some give when you really tighten the belt.
Mike, that could be the problem right there. At certain engine speeds, that extended arm could vibrate at its “natural frequency” and exhibit the fan belt motion you are observing.
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Dick Koch
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Re: Drive belt wobble

Post by Dick Koch »

Could be the v belt itself, you should carry a spare anyway. I have saved at least two Chevy's with my spare belt.
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