Alternator Bolt Troubles - Team Camaro Tech
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post #1 of 8 (permalink) Old Sep 7th, 03, 03:53 AM Thread Starter
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The alternator on my '69 Camaro - 350 engine keeps shearing off bolts. It's the bolt that goes through the top slide bracket that you tighten after tension is on the belt. I bought a chrome alternator and it came with a chrome 5/16" bolt. The bracket is a stock (non chrome). After a week of driving, the bolt broke right at the front (radiator side) of the bracket. I figured it was a cheap soft bolt so I replaced it with a non chrome 5/16" grade 8 bolt and after another week of driving, that bolt broke in the same exact place. The alternator looks to be aligned straight and the belt seems to be riding right in the center of the pulleys and the tension seems to be right (Not too tight). I thought of trying to use to a 3/8" grade 8 bolt but that would mean drilling out the hole on the chrome alternator and widening the slot in bolt slide bracket. I even tried watching for movement while revving the engine and everything looks good. The last time it broke, I heard the broken end of the bolt with the nut attached hit my fan and I'm worried that the next one may do some damage. I don't run the car hard and it's happened under normal driving. Has anyone had this same experience and if so, what did you do for a fix? Thanks! Bill
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post #2 of 8 (permalink) Old Sep 7th, 03, 04:09 AM
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Sounds like a case of over tightening the bolt. I don't see how a grade 8 bolt could break off that way unless it was twisted on installation- or not truly a grade 8 bolt. If you are sure that overtightening is not possible I don't have a clue why this is happening. I had a chrome alternator bolt just as you described but never had any trouble with it...


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post #3 of 8 (permalink) Old Sep 14th, 05, 08:14 AM Thread Starter
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Re: Alternator Bolt Troubles

This has happened again with another 5/16" grade 8 bolt. Any suggestions?
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post #4 of 8 (permalink) Old Sep 14th, 05, 08:32 AM
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Re: Alternator Bolt Troubles

too weird for me, I'd expect a grade 8 bolt to pull the threads right out of the alluminum alternator housing long before any damage happened to the bolt itself.





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post #5 of 8 (permalink) Old Sep 14th, 05, 10:26 AM
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Re: Alternator Bolt Troubles

It is transferring imbalance conditions and the place having the most effect is right at the bolt.

Make sure the top bracket is bolted in three places, two about the thermostat area and the adjustment place.

Also, check to see the bottom bracket is bolted in both places, the alt case and to eng block. And don't forget the bracket to the water pump.

Another thing you may want to do is use a large pattern flat washer, Gr 8, under the head, or replace the fastening assembly with a Gr 8 stud or a socket head bolt and flat washer.

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post #6 of 8 (permalink) Old Sep 14th, 05, 12:26 PM
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Re: Alternator Bolt Troubles

Take a look at the slot in the upper bracket. Run a file through the slot and clean up the edges, making them flat and/or rounded a little. The bracket may be cutting a groove in the bolts, making them weak.... then SNAP!!

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post #7 of 8 (permalink) Old Sep 14th, 05, 01:47 PM
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Re: Alternator Bolt Troubles

I might be way off here but did you hear the belt squealing at any time? It could be something locking up and there would be a lot of torque applied to the bolt. Just a guess worth checking.
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post #8 of 8 (permalink) Old Sep 14th, 05, 09:36 PM Thread Starter
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Thumbs up Re: Alternator Bolt Troubles

Thanks for all the useful info. I'll perform all those checks and post back what I find.
Thanks again! Bill
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