10SI to 12SI Alternator

[Ernest]

Im currently running, what seems to be the standard 10SI/61A alternator thats installed for the '79 model year commonly used with factory AC equipt, of which my car is and heater.

Lately while driving the malibu for my usual early morning 20mile sunday drives(weather permiting) just to keep the car in working condition since it is not a daily driver, i only drive it to car shows, swap meets, cars and coffee, etc., i've noticed the "check eng" and "battery" light is dimly lit off and on, no unusal noises, i'll have to have it checked.

In the mean time, im thinking about upgrading it to the 12SI alternator that puts out a little more power, like the 94A model, its for future upgrades, right now, im just running with standard headlights, parking lamps, brake light and turn signal bulbs, no LEDs of any kind, no radio or amp installed, no other power accessory, everything is manually operated.

I remember doing the same swap with a '75 chevelle hotrod i built back in the mid 90s, i removed the 10SI alternator that was factory installed and went off to a local junkyard and found some early to mid 80's model car and pulled the 12SI alternator of it, paid for warranty and i then had it tested at a local autozone, luckily it checked out just fine, and it worked like a charm since then.

Any thoughts about this one from amazon, the electrcal connections and the mounting postions shown are clocked the same as my current 10SI alternator, makes for a perfect match, or would i be better off just sticking with the 10SI 63A alternator.

https://www.amazon.com/GDSMOTU-Alternator-Compatible-1983-1988-Replaces/dp/B0CFQFBRKS/140-4090877-4341802?tag=gbody-20

 

[pagrunt]

I have a 12si on my my 350 instead of a 10si like it originally had. Just make sure you get on with a V belt pulley or just swap out the later crank & water pump pulleys for the wider belt.

 

[69hurstolds]

Do you have a "one wire" on it now? If so, do whatever as your wiring system is set up for it. If you don't, I wouldn't advise using the one-wire alternators on a street driven car, especially if it's not used often. Unless you put it on a float charger, aka battery tender. One wire alterators are a gimmick and do NOTHING to help out your car.

Get the 12SI as they're 78 A out the door, and possibly 94 A. They even have kits to do 140, however, unless you have a lot of power usage, I'd stick with the stock outputs.

 

[Ernest]

Still running original 3wire factory setup and would prefer to keep it that way, no mods.

 

[Clone TIE Pilot]

You may want to think about a CS130 instead, just get one with the proper clocking and swap a V belt pulley on it. The CS alternators puts out better at low RPMs than the SI series. I run a CS130 on my L69 305. Whatever alternator you go with, stay with a 3 wire setup.

 

[MrSony]

Another vote for the CS series.
I have a cs144 on my buick 350. Had to modify the brackets a bit, slice up the lower, extend the upper.

Regardless of which you go for, you can reclock them yourself. You don't have to play guess and check at a parts store or hunt for one trying to find one clocked right.
You can use a paper clip or some mechanics wire to keep the brushes pushed up when you put it back together if you accidentally pull the sides too far apart. You can usually pull the 4 bolts out just enough to turn the two halves.

 

[69hurstolds]

I'm still of the firm belief that you don't need extra amps unless you need extra amps (huge electric fans, spotlight bar, giant stereo amps, etc.). 3-wire stock setups sense wtf is going on in the alternator, and the amps you need up to max output (which you can check with an ammeter and small screwdriver/shorting device). I doubt anyone's stock system will need 78/94 amps. GM replacement alternators for G-bodies got upgraded to 94 amps early on. Not because they were automatically better, it's because they already started making a slew of them that would bolt in the earlier models, thus reducing the amount of different parts. Bean-counters, ya know.

One-wire systems MAY not self-excite at idle. They usually will start working if you rev the engine, but if you just crank it up and don't give it revs, there's no guarantee it'll be charging right away.

The CS130 bolts right in. But compared to a 12SI, they're not cheap. The wiring would need an adapter, either one with a resistor in it or one without. Usually the warning bulb on the dash provides enough resistance, but maybe not. Then you'd need to get the resistor adapter. I admit, I'm not a wire biter, so I'm not going down that rabbit hole.

Think about this. Answer the question of why do you think you need a more powerful alternator like a CS130? The General invested millions of dollars on electrical system design/development and if they thought 78A was good enough, doubling it doesn't make any sense. Granted, if you plan on future upgrades, and you do put one of those whamodyne monster alternators on, and you can sleep better, go for it. But your car's stock electrical system doesn't need it. If it does, you're just band-aiding a problem elsewhere in the system.

 

[Ernest]

As im sure the 10SI 63A alternator is sufficient for my current needs... factory AC, Heater, no radio, no power locks/windows/seats, no back window defroster, standard lights all around, no LED replacement of any sort.

Im thinking about the future... i would like to install the Edelbrock ProFlo 4 system at a later date, and that also requires an electric fuel pump, upgrade to a large single electric fan, or possibly two smaller units side by side, so i figure just the 12SI/94A alternator will do.

FYI... i had a chance to have the 10SI/63A alternator that came with the malibu checked out at a local Oreilys, its working like it should, and i scored 2ft of Gates 4219BG SAE 30R14TI 50psi fuel line hose for free because thats all that was left on the roll, i was looking to get 3ft total, and they couldnt sell what was left.

Im definately getting more of that fuel line, its just what every carbureted system needs today IMO, but at almost $5/ft, its pricey, and i also took the alternator to autozone for a second oppinion, the alternator checked out good there as well, theres a pinch of noise in one of the bearings when spun by hand, but nothing major, so im not really worried about it at this time.

 

[olds307 and 403]

The 12SI is a no brainer and a super easy swap. Just male sure it is a true 12si, many are a 10SI with an upgraded fan or a 1 wire. There is a 88 Cutlass CS 130 105 amp option out there, I had one on my 88 Cutlass, a Champion/Remy reman.

 

[69hurstolds]

There is a 88 Cutlass CS 130 105 amp option out there, I had one on my 88 Cutlass, a Champion/Remy reman.

??? This is new. I have not heard of an 88 with a factory CS130. AFAIK, the 88 Cutlass RWD came with a 78A alternator, 12SI.

87 had a 1st and second design. 1st design was a carryover from the 84-86 p/n 1105565, 12SI. 2nd design was used in the last part of 1987 all the way to the end for the 88 models, p/n 1101303. Only difference I can discern between the two was they used different capacitor (for noise reduction) p/n and the screws that hold the front bearing retainer plate are different part numbers.

As for 12SI and 10SI, the 12SI has a ridge on the front of the frame end housing to fit behind the plastic fan for better air movement, as well as different and bigger intake vents in back. Many pieces CAN interchange, and some can't, but why would you? The 12SI makes more heat and needs better ventilation.

The big azz vents in the back and the big plastic fan are a dead giveaway for ID'ing the 12SI.

And the "ridge" discussed earlier (10SI didn't have the ridge):