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Drive belt wobble

Posted: Thu Jun 16, 2022 5:01 pm
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.

Re: Drive belt wobble

Posted: Thu Jun 16, 2022 11:10 pm
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.

Re: Drive belt wobble

Posted: Fri Jun 17, 2022 3:57 pm
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.

Re: Drive belt wobble

Posted: Fri Jun 17, 2022 4:01 pm
by vanguy16
Imagine that wobble being 20-30 times faster as the camera smooths it out so to speak.

Re: Drive belt wobble

Posted: Fri Jun 17, 2022 5:25 pm
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

Re: Drive belt wobble

Posted: Fri Jun 17, 2022 5:30 pm
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

Re: Drive belt wobble

Posted: Fri Jun 17, 2022 5:52 pm
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.
Thanks,
Dick.

Re: Drive belt wobble

Posted: Fri Jun 17, 2022 5:56 pm
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.


Re: Drive belt wobble

Posted: Sat Jun 18, 2022 6:52 pm
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.

Re: Drive belt wobble

Posted: Sat Jun 18, 2022 7:39 pm
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.

Re: Drive belt wobble

Posted: Sat Jun 18, 2022 9:39 pm
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.