1980 correct alternator?

**Joe L.** · June 9, 2006, 07:23 PM

Re: 1980 correct alternator?

Theo-----

Well, I did give you the wrong information. That's because several other sources had given me the wrong information over the years and I had accepted it as "fact" without further checking/corroboration. Further research has now convinced me that these other sources are incorrect. Here's what I now believe: all 1969 through 1982 Corvettes originally used either a 10 SI series alternator or a 15 SI series alternator. None used a 12 SI series alternator, although other GM cars of the period did.

So, the original alternator for your 1980 was a 15 SI alternator, likely of either GM #1101041 or 1101075. This is if you have K73, which I think is the RPO code you were referring to.

By "correct" alternator I don't know just how correct you mean. If you mean "numbers" and "dates" correct, that's one thing. In that case, you'll need to start looking around. I don't think that it will be really difficult to come up with one of these, though.

If you mean configuration-correct, but not necessarily "numbers" and "dates" correct, it's no problem, at all. You can get a re-manufactured unit easily from Delco. These are a 70 amp unit. I would think that a 70 amp unit would be sufficient for your application, even with your added electric fans.

If you want more amperage, you might be able to use a GM #10464391. This is a 97 amp unit. I believe that it's a 15 SI, but I'm not 100% sure. It could be a 17 SI.

**theo law** · June 10, 2006, 09:31 AM

Re: 1980 correct alternator?

Hi Joe
Thanks very much for getting back to me about this. As I said before, I'd left my search to go cold for a while, as I had more pressing issues on the car. Coming back to it, I was initially just as confused as last time, but it begins to look like we've cracked it now! At the time, I had read loads of conflicting information about the 10/12SI and didn't even know of the existence of this 15SI. The part #s you quoted are exactly what I had thought, I believe the ..041 is the early production and ..075 the late - my vette, being 3rd July 80, would be late, I guess??
And yep, I have K73! I'm glad you've responded personally, I didn't want you to think I was deliberately trying to be contradictory, I was cautious about going against your quite frankly scary knowledge!
If you go to the delco website and x-ref that ..075 number, you get the part # of a reman delco unit (forget the # right now) I then found a delco pdf document that lists loads of SI part numbers with their amperage, designation and "clock" config. It clearly gives the delco x-ref number as a 15-SI 70A unit. That's where my recent bout of confusion started, and why I posted here.

Strangely, the vette part microfiche, which I downloaded on pdf from somewhere, lists the correct number as 1101070 instead of 1101075, perhaps that's just a typo??

As for correctness, I wanted to try and find an alt that looks correct in the engine bay for the period, as I said I'm not into judging otherwise I would never have fitted the fans, but I like to keep things looking period where possible. That's why I needed to know the series - with that knowledge I could then see how far one can safely upgrade a 15SI, above 70A. The problem is that with lights and fans and other stuff, I bet I need upwards of 40-50 A at idle, which may be optimistic even with an upgraded 15SI, but of course I would never have actually known without first finding out what the benchmark part was!

So ideally, I'd like to find a correct # and date 1101075, but before I do, I can now get in touch with the alt. parts places and see how much potential there is for beefing these things up!

Have you any idea where one might track down such an alt? obviously condition isn't too important, as I'd be restoring anyway. I hope the relative newness of the 80 might play in my favour!

Thanks again Joe, really appreciate your help!

Theo

**Joe L.** · June 10, 2006, 01:03 PM

Re: 1980 correct alternator?

Theo------

Given your car's date of manufacture, I think that it's safe to say that it falls into the "late production" category and, therefore, originally had the '075' alternator installed.

The GM #1101070 is the alternator that GM once-specified as the SERVICE alternator for your application. The GM #1101075 was never available in SERVICE. I don't know what the differences are between these 2 alternators. I expect it's minimal, if any. It may even be that when one purchased the GM #1101070 alternator, one found that was the number on the box, but the unit inside had the 1101075 number on it. I doubt it, but it's possible. It's also possible that the only difference between the '070' and '075' is the fan/pulley. I believe that the '075' unit supplied to PRODUCTION had the fan and pulley already installed. I expect that the 1101070 had no fan and pulley installed. This would make the 1101070 applicable to many more applications than a unit that had an application-specific fan and pulley on it. The installer simply transfers the fan and pulley from the old unit to the new unit. Still, the stamped numbers on the case would be different even though the basic alternators were identical.

The 1101070 was a NEW alternator, not a re-manufactured unit. It's been discontinued for quite some time as GM no longer sells new alternators for these older applications. Re-manufactured is the best you can do through GM. However, it does give you a CHANCE, albeit a small one, to actually get the part number and date you need. Unless, of course, Delco now obliterates the original numbers on their rebuilt alternators as some rebuilders are starting to do.

In general, the "route" to increased amperage on these Delco SI series alternators is through changing the stator. I don't know if an increased amperage stator is available for the 15 SI which would boost the output above 70 amps. I think that there is one, though. 70 amps is, basically, the "bottom-of-the-rung" as far as 15 SI units go. So, I think that you can go higher in amperage and still stay within the 15 SI case architecture.

For an original part number and date alternator you might try contacting John Pirkle. He does rebuilds and restorations of Corvette alternators and other electrical parts. He has a pretty good inventory of units. He can't be of too much help with some of the "rare and sought after" units, but I don't think that the one you're after falls into this category (YET!). He can also advise as to upgrading the amperage output.

**Theo Law** · June 11, 2006, 04:21 AM

Re: 1980 correct alternator?

Joe,

Ah, that makes sense, I just wondered why there was a discrepency between those numbers.
I've already started looking into suppliers of upgrade kits for the 15SI (now I actually know that's what it is!) and I've seen stators up to a 105A rating. Have made some inquries into any potential for higher output, but of course cooling becomes an issue.
I'd like to try and find out how these units perform at idle, which is of course where those 30A fans are most likely to kick in. On a hot summer night with the headlights on, I really need that alt to give a good solid output at/near idle. We'll see what the suppliers say.
I'll also get in touch with Mr. Pirkle to see about a core unit. As you say, I don't think this one is quite "rare and sought after", which could be a bonus, or could work the other way! Quite honestly, the whole "shipping to the uk" issue is probably going to be the killer, so I'll obviously try my luck over here too, not that I honestly expect much to come of it. So much more choice on your side of the pond!

Your help here has been invaluable Joe, thanks very much indeed. I'll post back if I get any more information.

Cheers!
Theo

1980 correct alternator?

1980 correct alternator?

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