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Alternator upgrade for 1978

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gmule

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I must be a search idiot. I can only imagine that this question has been brought up at least a 100 times but I can't seem to find it with my querry.

Anyhoo does anyone know what alternator can be swapped into a 1978 to replace the stock 63 amp alternator with something like 100 or more amps?

I need the extra juice to run the plow and lights.

Sorry for asking such a routine question.
 
gmule said:
I must be a search idiot. I can only imagine that this question has been brought up at least a 100 times but I can't seem to find it with my querry.

Anyhoo does anyone know what alternator can be swapped into a 1978 to replace the stock 63 amp alternator with something like 100 or more amps?

I need the extra juice to run the plow and lights.

Sorry for asking such a routine question.
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Well I had a 1991 crew cab with a 350 TBI and a standard V belt 100amp alternator.
It was stock so I am sure that one will work.
Another choice I put before is a Cadillac 85 or 87 alternator that was a 105amp.
 
Thank you I have been reading for hours going down the rabbit holes on Stereo needs and modified bracktery etc, etc,
 
When I did mine I checked with the local electronics guy and he said that a stock alt out of a 80's ish Cadillac would fit and it was 105 amp i believe. IIRC its a 12si.
 
Orange Bomber said:
When I did mine I checked with the local electronics guy and he said that a stock alt out of a 80's ish Cadillac would fit and it was 105 amp i believe. IIRC its a 12si.
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Thanks for that info, searching for a 12si nets me a new alternator at summit for 90.00
How cool is that?:woot:
 
gmule said:
Thanks for that info searching for a 12si nets me a new one alternator at summit for 90.00
How cool is that?:woot:
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Yeah it's a 12SI but be carefull, they had them from 37 amps up to 105 and Vbelt or serpentine, so make sure you get the right apllication.
I got mine from Kragen at the time 105amp for $105.
I had it in my hand and made usre it was rigth, I had to unbolt the case and rotate 1/4 turn for my plugs to be in the right position.
 
gmule said:
This little tidbit is great to know
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Yeah lots of GM cars and trucks were equiped with the 10SI and 12SI which have the same dimensions, and each vehicle had different requirements for routing wires so they did come in different configuration but all you need to do is take off the 4 long thin bolts, and carefully rotate the halves to align same as your vehicle, everything else would be the same.
The 12SI are the later design and seem to have better quality and came in higher amps.
 
I have found this outfit has lots of information.
http://www.alternatorparts.com/index.htm

Also lots of alternators if you want some really big amp outputs.


NOTE: I have never dealt with them, or know anybody who has, but they do have good information.
 
i have the summit 100 amp single wire unit.works good and have had it 10 years without a problem.just tell them what year you have and they send you what fits.
 
gmule said:
Just to be sure the 10si alternator and the 12si alternator use the same wiring correct?
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yes
The difference externally is the fan on the pulley the 10SI is the angled steel blades, the 12SI has a plastic fan covered with a steel plate
 
I copied and pasted this from another post I made a while back.

Avery4jc said:
Madelectrical.com is a good resource for learning about your electrical system. I lost my alternator on our last wheeling trip and spent an afternoon reading up on that site and learned quite a bit. I ended up going to NAPA and bought one of these off the shelf, it's 94 amps and bolts right in place.

12SI, 94 amp, at 3:00 (AC-DELCO # 321-266, Lester #7294-3)

Tell the auto parts counter person that “The alternator is for a 1984 High performance Chevy Camaro, with 5.0L (305G) engine, 94amp alternator
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Thanks for all the good information everyone. Got the new alternator installed today now I'm off the the salvage yard for a drivers side battery tray for the second battery.
 
gmule said:
Thanks for all the good information everyone. Got the new alternator installed today now I'm off the the salvage yard for a drivers side battery tray for the second battery.
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If you don't find one I have a few :thumb:
 
It's a good idea to either upgrade the 10 ga red wire that goes to the stud on the altenator to the fusible links at the starter solenoid--,or add another 10 ga. wire to that stud and run it to the positive battery terminal,because the old wiring is often corroded or damaged,and the increased amperage will tend to fry the bad spots and or restrict the current flow to the battery and rest of the truck due to its high resistance...even if its in good shape,it may not like handling double the original amperage it was designed for..
 
I had already taken care of those issues. It seems that somewhere along this trucks life someone went a little nuts with butt connectors and electrical tape just hacking and splicing in random fashion. It's not like the trucks from the 70's had that much wiring to begin with.

My problem is now that I have gotten started on this thing where will it end? I originally wanted a plow truck but I think it is going to end up being a nice plow truck when I get done. The fact that my wife digs the step side is a bonus.
 
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