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Old 04-03-2021, 03:24 PM
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Default 80 amp alternator bracket questions

Ok......working on a 73......that originally came with AC...so should have had the big alternator.........

Original engine with alternator brackets were long gone....but PS pump and brackets remain..

I'm test fitting what I believe should work....and hood is just touching the top of alternator bracket...when closed.

As I recall....71-74's used an idler pulley on the 80 amp....

I'm using a 75 as a blueprint.....(no idler)......and the hood seems to have clearance...but is a Formula hood...not steel...

Looking for some input..............Thanks

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Old 04-03-2021, 06:45 PM
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Yes, there is an idler pulley and I can look for some pictures or take some tonight when I get home and post back. I might have some of the idler pulley brackets and an idler pulley.

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Old 04-03-2021, 07:03 PM
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Have a fairly deep stock of '80 amp pieces, if struggling to come up with pieces.

Several PY members have been taking the more common 80 amp front alt mounting plate that has the long adjustment in it, then they have cut the adjustment slot down, carefully welded the two pieces back together & touched the welds up with a grinder. This slightly sectioned front adjustment slot allows the elimination of the idler pulley assembly & the installation of the 80 amp alt while having enough adjustment, & creating slight clearance under the hood which is critical in a Firebird.

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Old 04-03-2021, 08:20 PM
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I thought the 80A alternators were only used with rear window defrosters? I'm talking about the resistance wire ones glued to the glass, not the mechanical blowers.

A/C just meant you got a 55A alternator instead of a lesser one.

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Old 04-03-2021, 08:31 PM
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I believe you could get AC or heated back glass......with the small case alternator...but if you ordered both....the large case (80 amp) was required.

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Old 04-03-2021, 11:05 PM
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There was 3 ways to get a mandatory 80 amp alternator as far as I remember. I have owned a few '73's with a 80 amp set up stock.
1. A/C + Rear "GRID" defogger
2. A/C + Power windows
3. A/C + PW, and Rear Grid Defogger
All had a idler, which GM changed over the years. All had a STATIONARY big case Alternator, with its own brackets. You may want to do a search using the words "80 amp" on this forum, there are many pics and
information here that has been discussed.
Good luck!

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Old 04-04-2021, 11:32 AM
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Why not use the alternator off a '90 Corvette? Pretty much a direct bolt on replacement for a 10SI and puts out 100 amps at an idle. No need for for bracket change or idler pulley. For the plug there are adaptors or you could just re-pin.

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Old 04-04-2021, 01:45 PM
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Quote:
Originally Posted by FrankieT/A View Post
Why not use the alternator off a '90 Corvette? Pretty much a direct bolt on replacement for a 10SI and puts out 100 amps at an idle. No need for for bracket change or idler pulley. For the plug there are adaptors or you could just re-pin.
That's a great idea for a hot rod.......but no import parts on this car.......

Gotta look stock....

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Old 04-04-2021, 01:56 PM
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Default Pictures of 80 Amp Alternator Idler Pulley

Here are some pictures of mine installed on my '73.
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Old 04-04-2021, 02:07 PM
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Default More Pictures of 80 Amp Idler Pulley brackets

Sorry, I don't know why the pictures are sideways, but here are some more and of a set up I have, it was restored by Super Car Specialist. Bearing in the pulley was still shot after the restored everything, so I made tooling so that I can now replace the bearings, so I replaced the bearing with a double sealed bearing compared to the original single seal. The single seal allowed all the grease to come out and collect inside the pulley.
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Old 04-04-2021, 02:11 PM
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Default Pulley Bearing

Here is a picture of the double sealed bearing installed and one I did about 10 years ago.
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Old 04-04-2021, 02:17 PM
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Quote:
Originally Posted by Pepi View Post
Sorry, I don't know why the pictures are sideways, but here are some more and of a set up I have, it was restored by Super Car Specialist. Bearing in the pulley was still shot after the restored everything, so I made tooling so that I can now replace the bearings, so I replaced the bearing with a double sealed bearing compared to the original single seal. The single seal allowed all the grease to come out and collect inside the pulley.
Thanks...for posting all the great pics...

I will look into upgrading the bearing...once we are up and running.....

What I need to see at this point is a "naked" picture of the front alternator bracket...which I believe to be a 9790679......


I will try a search here and see what comes up.


Last edited by Green Hornet; 04-04-2021 at 02:55 PM.
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Old 04-04-2021, 02:30 PM
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Here is a pictures of NJSteve's 73, not a naked bracket, but somewhat shows the front being fixed position.

If you have the idler pulley and need the bearing replaced, send me a PM if you want. As I mentioned, I made tooling to be able to remove old bearing and replaced it with a better bearing. I have done several for some members here.
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Old 04-04-2021, 08:05 PM
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Quote:
Originally Posted by Green Hornet View Post
That's a great idea for a hot rod.......but no import parts on this car.......

Gotta look stock....
I wouldn't exactly call a Corvette an import...Granted it looks a little different than a 10SI, but when you put your stock fan and pulley on its pretty close. To each his own...

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Old 04-05-2021, 12:34 AM
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Quote:
Originally Posted by Pepi View Post
Here is a pictures of NJSteve's 73, not a naked bracket, but somewhat shows the front being fixed position.

If you have the idler pulley and need the bearing replaced, send me a PM if you want. As I mentioned, I made tooling to be able to remove old bearing and replaced it with a better bearing. I have done several for some members here.
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