Busted Alternator Bolt

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crpntr78

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If the long bolt pictured is the one that sheared off, I'm thinking there's only a thread or two in the head. Shouldn't be too hard to back that broken piece out.
 

C10_Blackie

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Hmmm, mine have never had that, just a spacer that the bolt goes through.
It is really hard to see, but mine looks more similar to hers. I don't know the names of things so have to make stuff up as I go, so what I'm going to call the 'tensioner' bracket is fixed to the head and then a bolt attaches the bracket to the alternator with a bolt that allows it to slide and tension the belt.

So then there's one an only other bolt that acts as the pivot on the bottom. On mine, the bolt slides through a bracket that is also connected to the head, then through a sleeve on a bracket that is attached to the alternator, then into the head, so at that point the alternator is attached both for and aft and is in there there as good as it will never need to be.

So mine as it sits is attached to brackets that are attached to the head very solidly at two points and that bolt I added is definitely doing something - just nothing I'd want on any longer than needed. And not surprised that this is other than standard: my truck originally had a 305 in it and a former owner threw this 350 in it with the carb and headers and it looks like they legoed everything in there however it seemed convenient. Ripped out the A/C and trans cooling lines while they were at it so I'm going to be correcting things on this truck for years to come. But then I did say that I wanted a hobby...
 

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If the long bolt pictured is the one that sheared off, I'm thinking there's only a thread or two in the head. Shouldn't be too hard to back that broken piece out.
Let's hope that is the case. If I hadn't been able to come up with a temporary solution the next thing I would have tried was some more penetrating oil and a screw extractor before giving up, but the way bolts tend to seize up in heated applications made me doubtful that anything other than drilling it out was going to work and at that point I'd call for a professional-type adult before I ended up making things worse (and I'm speaking from experience here).

That is a good thought, though: I'm sure that's the original bolt so finding out the original length would be easy and it wouldn't be hard to know exactly how much is left stuck in there.
 

C10_Blackie

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And here I was thinking that I was just going to enjoy many years of mostly bolting new aftermarket parts on. I'm almost glad the truck decided to remind me that stuff like this happens. And that was the last time I go anywhere in this truck without a good selection of tools.
 

SirRobyn0

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@C10_Blackie Will it make it to the shop is a hard thing to answer, but @DoubleDingo gives good advise. If the battery is charged up and you run without lights and heat you won't drain the battery and will minimize load on the belt. My concern would be the bolt backing out and hitting the fan, especially at RPM where the fan might throw that bolt into something like the radiator or the hood. With that sad if it were me I'd try to secure everything as best I can and drive it, but with the knowledge it might end in a tow.
 

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Hmmm, mine have never had that, just a spacer that the bolt goes through.
did it have a 12si? i could be wrong but im not sure if the 12si has a threaded hole in the same spot for that
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The bolt is going the wrong way, the alternator case of a 10si rests up against it, and it bolts on. Ive only seen that bracket the OP has (same as mine) with those. WHats your engine sourced from?
 

AuroraGirl

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It is really hard to see, but mine looks more similar to hers. I don't know the names of things so have to make stuff up as I go, so what I'm going to call the 'tensioner' bracket is fixed to the head and then a bolt attaches the bracket to the alternator with a bolt that allows it to slide and tension the belt.

So then there's one an only other bolt that acts as the pivot on the bottom. On mine, the bolt slides through a bracket that is also connected to the head, then through a sleeve on a bracket that is attached to the alternator, then into the head, so at that point the alternator is attached both for and aft and is in there there as good as it will never need to be.

So mine as it sits is attached to brackets that are attached to the head very solidly at two points and that bolt I added is definitely doing something - just nothing I'd want on any longer than needed. And not surprised that this is other than standard: my truck originally had a 305 in it and a former owner threw this 350 in it with the carb and headers and it looks like they legoed everything in there however it seemed convenient. Ripped out the A/C and trans cooling lines while they were at it so I'm going to be correcting things on this truck for years to come. But then I did say that I wanted a hobby...
i took my bracket off a 78 305 but I also had the originals like it, just were rustier. But those were from a 77 350(car) Lol.
 

Ricko1966

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I hate to keep dragging this thread out. But this is kind of relevant. The bottom bracket you are using,I know of one gmsb member that I respect who is using 2 of those brackets,stacked and welded together for extra rigidity. No sleeve no bolt in the head. Not Ideal,but just in case your shop guys determine the broken bolt is beyond what they want to tackle.
 

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Sweet! I have never seen one like that. I learned something today, now I can go home. Now I need to check out my factory 81 to see if has that style
 

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Quick follow-up: I made it to the shop, but just barely. I did a couple of short test drives and my temporary fix held just fine but when I set out on the actual trip to the shop it dropped the belt in the first couple of miles. I didn't notice anything much with the gauges until I was on the freeway when the temp started to climb and by that time I was in heavy traffic in a construction zone. The battery held beautifully and I only needed to stop once to let it cool down.

I have no clue as to why that belt came off. It certainly wasn't too loose so maybe it was too tight. Was a bit of a white-knuckle drive as that temp gauge went up but I got there and since the motor is an unknown quantity we can do with an integrity test anyway, I guess. One thing for sure is that the drive home is going to be a lot better than the drive out was.
 

Ricko1966

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Quick follow-up: I made it to the shop, but just barely. I did a couple of short test drives and my temporary fix held just fine but when I set out on the actual trip to the shop it dropped the belt in the first couple of miles. I didn't notice anything much with the gauges until I was on the freeway when the temp started to climb and by that time I was in heavy traffic in a construction zone. The battery held beautifully and I only needed to stop once to let it cool down.

I have no clue as to why that belt came off. It certainly wasn't too loose so maybe it was too tight. Was a bit of a white-knuckle drive as that temp gauge went up but I got there and since the motor is an unknown quantity we can do with an integrity test anyway, I guess. One thing for sure is that the drive home is going to be a lot better than the drive out was.
Sir look back at post #2 where I said if your power steering belt is spinning your fan and waterpump,you won't have a problem. If the power steering belt is spinning your fan and water pump and your engine was getting hot,you have another problem. Take a look, see if you have a belt other than the alternator belt spinning the water pump.
 

RustyPile

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I'm probably arriving late to this party, but that broken bolt is an easy repair. As a mechanic for over 30 years, I have seen quite a few of those same broken bolts.. Using the following technique, I've had 100% success at removing the broken piece from the head.. Disconnect the POS battery cable and remove the alternator and all associated brackets to gain unincumbered access to the broken bolt.. There's plenty of "meat" around that threaded hole.. Using a die grinder and a small diameter and very thin cutoff wheel, cut a slot across the center in the end of the bolt. You'll cut into the head a bit, but that won't hurt anything.. Cut the slot about 1/16" deep into the bolt..

Here comes the good part. Put a flat blade screwdriver in the slot and "unscrew" the broken piece.. It should come out easily because the bolt, when tightened, doesn't bottom out in the hole.. Obtain a new grade 8 bolt and put everything back together...
 

RustyPile

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@C10_Blackie We're all curious, I sure am.. How did this project turn out?? Did you pay that shop an arm and a leg to remove that broken bolt and replace it, or, were you able to repair it yourself???
 

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