Internally Regulated Alternator Questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**71CHEVYSHORTBED402** · 01-29-2021, 01:48 PM

Working on a 1971 402 with A/C. It's going to be factory less an HEI, mini-starter, ditching the TCS and the external regulator. Amp requirements are limited.

The truck gets all new wiring anyway, which can be customized to suit. I believe the wire requirements for the 12SI & CS144 differ slightly.

I'm green where it comes to wiring. I know there's a three wire or one wire system, perhaps that can be done with the same internal regulated alternator, not sure. Only thing I know is simple preferred and I'd like to use the original brackets and pulleys if that's possible.

I was recommended an 12SI or CS144. Looks like the 12SI (100+/- amps) is the older version, I'm leaning to that. From what I'm reading appears the CS requires a different bracket(s).

Assuming the 12SI is the right direction for this application, will the original pulleys and brackets work with that alternator? Also, can anyone recommend what 12SI to purchase, part number or applications?

Any input appreciated, thank you.

Andy4639 · 01-29-2021, 11:38 PM

Not sure about BB alternator. I have done plenty of SMB changes but not the BB.

I would contact Mad electric and get them to answer this. The 3 way system is much better over all. It should be easy enough to do if you are using a complete upgraded wiring harness.
I would think everything would bolt up if you stay with the SI type alternator. Just like on SMB motor. If your truck is pretty much stock a 140 amp should be fine are even a 200 but they are price though.

Dead Parrot · 01-29-2021, 11:40 PM

Assuming the motor came with a 10DN alternator(externally regulated), the 12SI has the same mounting holes and case size. The wiring is different between the old 10DN and 12SI but since you are installing all new wiring, doesn't matter.

Here is an informative link: http://www.madelectrical.com/electri...elcoremy.shtml

IMO - you are better off with the three wire setup as you can run the voltage sense wire to your main junction block so the alternator can compensate for any voltage loss in the main feed wire from the alt to the block.

**VetteVet** · 01-30-2021, 12:14 AM

you may find all your answers in the electrical FAQs thread at the top of the page in the electrical forum.

**71CHEVYSHORTBED402** · 01-30-2021, 01:04 AM

Quote:

Originally Posted by VetteVet

you may find all your answers in the electrical FAQs thread at the top of the page in the electrical forum.

Oh look, the guy who recommended an 12SI or CS144

Nice to hear from you Vet, I'll check that page.

Thanks for all the input.

Here's some cross references, I believe I need an alternator for a 85 Firebird

https://bzerob.com/library/gm/gm-altpartno.html

RustyPile · 02-03-2021, 04:10 PM

The engine is simply the mechanism used to spin the alternator, it doesn't matter about whether it's a BBC, SBC, or I6... A 12SI will bolt right up where the 10DN resided, and with the proper wiring modifications, it will work just fine.. As for what specific automobile the alternator comes from, just grab the nearest 12SI on the shelf and follow the clocking instructions posted here: http://67-72chevytrucks.com/vboard/s...d.php?t=816728

**71CHEVYSHORTBED402** · 02-12-2021, 11:56 PM

Quote:

Originally Posted by RustyPile

The engine is simply the mechanism used to spin the alternator, it doesn't matter about whether it's a BBC, SBC, or I6... A 12SI will bolt right up where the 10DN resided, and with the proper wiring modifications, it will work just fine.. As for what specific automobile the alternator comes from, just grab the nearest 12SI on the shelf and follow the clocking instructions posted here: http://67-72chevytrucks.com/vboard/s...d.php?t=816728

What I've heard since, less clocking. Thank you for the link.

01-29-2021, 01:48 PM	#1
71CHEVYSHORTBED402 Senior Member Join Date: Feb 2009 Location: Northern Nevada Posts: 7,118	Internally Regulated Alternator Questions Working on a 1971 402 with A/C. It's going to be factory less an HEI, mini-starter, ditching the TCS and the external regulator. Amp requirements are limited. The truck gets all new wiring anyway, which can be customized to suit. I believe the wire requirements for the 12SI & CS144 differ slightly. I'm green where it comes to wiring. I know there's a three wire or one wire system, perhaps that can be done with the same internal regulated alternator, not sure. Only thing I know is simple preferred and I'd like to use the original brackets and pulleys if that's possible. I was recommended an 12SI or CS144. Looks like the 12SI (100+/- amps) is the older version, I'm leaning to that. From what I'm reading appears the CS requires a different bracket(s). Assuming the 12SI is the right direction for this application, will the original pulleys and brackets work with that alternator? Also, can anyone recommend what 12SI to purchase, part number or applications? Any input appreciated, thank you. __________________ Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assm. guide "kit" for restoring it from ground up. With assys, the guide accts for 1000s of OEM identifications and part numbers, all written in short order. 700+ images include assm, illust., charts, and points of interest. Much of the info. applies to all 67-72 GM trucks, and to a lessor degree all 67-72 GM vehicles. My build thread, and more on the guide https://67-72chevytrucks.com/vboard/...d.php?t=730025

01-29-2021, 11:38 PM	#2
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Internally Regulated Alternator Questions Not sure about BB alternator. I have done plenty of SMB changes but not the BB. I would contact Mad electric and get them to answer this. The 3 way system is much better over all. It should be easy enough to do if you are using a complete upgraded wiring harness. I would think everything would bolt up if you stay with the SI type alternator. Just like on SMB motor. If your truck is pretty much stock a 140 amp should be fine are even a 200 but they are price though. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

01-29-2021, 11:40 PM	#3
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,472	Re: Internally Regulated Alternator Questions Assuming the motor came with a 10DN alternator(externally regulated), the 12SI has the same mounting holes and case size. The wiring is different between the old 10DN and 12SI but since you are installing all new wiring, doesn't matter. Here is an informative link: http://www.madelectrical.com/electri...elcoremy.shtml IMO - you are better off with the three wire setup as you can run the voltage sense wire to your main junction block so the alternator can compensate for any voltage loss in the main feed wire from the alt to the block.

01-30-2021, 12:14 AM	#4
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,703	Re: Internally Regulated Alternator Questions you may find all your answers in the electrical FAQs thread at the top of the page in the electrical forum. __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

02-03-2021, 04:10 PM	#6
RustyPile Registered User Join Date: Dec 2017 Location: Elkhart, Texas Posts: 1,526	Re: Internally Regulated Alternator Questions The engine is simply the mechanism used to spin the alternator, it doesn't matter about whether it's a BBC, SBC, or I6... A 12SI will bolt right up where the 10DN resided, and with the proper wiring modifications, it will work just fine.. As for what specific automobile the alternator comes from, just grab the nearest 12SI on the shelf and follow the clocking instructions posted here: http://67-72chevytrucks.com/vboard/s...d.php?t=816728



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