1956 Buick Alternator Conversion

[Beemon]

I don't think anyone has actually put one of these together for an alternator. A lot of threads on theory, ideas, etc but nothing too in detail. The nice thing about this conversion, as I tend to do with all my musings, is to leave the bracket stock. This, of course, posed some interesting problems which I was eventually able to solve through research, perseverance and the in-guy at NAPA. This write up is for a GM 10si 63 amp alternator. 63 amps is kind of an understatement as the max output of 63 is at 7000 RPM and I'll never see that. At 2000 RPM, the output is 55 amps so not too bad. A solid 35 amps at idle. The one I bought was new from NAPA for $68. Part # NNE 1N4011A. I wanted to avoid remanufactured alternators for obvious reasons. I also picked up the pig tail for $4 so the wire connection was idiot proof. Part # ECH VRC148.
 

 

The first issue was the saddle style mount of the original generator vs the thru mount of the 10si alternator. 27si alternators were available, but the cost was a bit much and I wanted to keep close to 30-35 amp output under normal driving. When I decided on making the alternator work, I started taking measurements. The bracket ear is 1/8" thick and the generator leg is 3/8" thick. The alternator pulley must be then offset 1/2". To mount, I used an 8" bolt with an aircraft grade lock nut on the end so no amount of vibration will let it fly loose. I used 5 1" 5/16" ID steel spacers from the hardware store, but had to cut 1/8" off to space the alternator all the way forward. The stock wiring harness was already 10g, which is what GM used as stock. I taped off the pink wire and grounded the alternator with the yellow wire just like the generator. For the plug, the #2 plug wire (red) needs 12v to regulate amperage, so I jumped it to the battery terminal on the back. The #1 plug wire (white) is the exciter circuit and needs switched 12v.

 

 

About the exciter wire: without a resistance wire and a dummy light, voltage from the ignition switch can back feed from the alternator into the coil and keep the engine running while the ignition is turned to off. To circumvent this issue, I installed a 1N5408 rectifier diode in line, connected with butt-connectors and wrapped in electrical tape. The gray line on the black silicon diode faces the alternator. This keeps current flowing only to the alternator and does not allow back feed to the coil. Don't ask me about the diode specifically, I found it on a tractor forum and it works.

 

 

I opted not to install a dummy light. I figured it was either going to work or be sent back to NAPA after I confirmed with the multimeter. The white exciter line goes straight to the 12v hot side of the ballast resistor.

 

 

By now you're probably wondering about pulley alignment. A single groove pulley was not going to cut it by any means, so I had to get crafty. My go to guy at NAPA happened to have a spare 2 groove pulley, otherwise I was going to purchase this other alternator that came with a 2 groove pulley. Part # RAY 2134031. The only difference is that instead of the clock being 12:00, it's at 3:00 so wiring may be a little bit more difficult. Pulleys are pretty rare but if you know a local rebuild shop that does nothing but alternators, starters, etc., they might have one. Despite the 2 groove pulley, I had to pick up a 16mm washer to space the pulley 1/8". The second groove on the pulley was 3/8" from the first groove, so this took up the 1/2" deficit that was left by the bracket shift. To be clear, both pulleys on the generator and alternator 1 groove were the same height.

 

 

Pulleys are aligned and checked with a straight edge off the back of the water pump pulley. The only thing that bugs me is the empty pulley, but it was either that or custom fit a bracket (don't have the shop to do it, aiming for simplicity), a bracket off a late 401/425 without AC (mounts to the head which requires the permanent removal of the spark plug cover and may or may not interfere with generator mount), or leave the generator be.

 

 

Wiring on the other side was simple. Move the white 10g wire from ARM to BAT terminal on the voltage regulator so it runs through the amp meter.

 

 

The green wire that attached to the starter relay was removed and taped off. I added a new wire and grounded it to the other screw on the side of the junction block.

 

I did this conversion because I had a suspicion that the generator had been holding back more than just accessories. After first test fire, the car immediately came to life with no ignition hesitation. Brighter dash lights, headlights. Multimeter had shown a full 14.7V at idle, the generator was maybe 13.6V. When the engine was shut off, the battery remained at around 12.7V with no drain. With the ignition switch on, there is a slight drain, but that's due to the exciter circuit I'm pretty sure. This is an interim thing until I can afford a Powermaster Powergen alternator. I plan to go to power windows and electric wipers (the 55 chev motor is on the way). The extent of my sound system will be a solid state radio with stock speakers. Can't think of anything else at the moment, but no more issues with charging.

 

Anyways, I hope this helps someone out.

[MrEarl]

Great job Benjamin, on both the alternator work and the write up! Thanks! 

[mackensen]

Question. Where did you connect the other end of the wire you connected to the terminal on the junction block? Is it from the starter relay to the junction block?

Edited August 24, 2018 by mackensen
add info (see edit history)

[MrEarl]

On 1/21/2017 at 4:06 AM, Beemon said:

Anyways, I hope this helps someone out.

 

☝️you got a question Benjamin

[Beemon]

On the back of the alternator, from the pig tail I ran the white wire to the ignition switch ballast resistor. If I were to do it again, I would have rather ran it to the starter relay as it is also switched 12V. The red wire I jumped to the battery lead on the alternator. From there, I used the stock yellow wire to ground to the alternator case and the stock white wire to the alternator battery terminal. Tape off the pink wire, its useless now. On the voltage regulator, you need to move the white wire from armature to battery, where the red wire is. This is important, you will have to cut the green wire off the white wire's spade connector. Disconnect the green wire from the starter relay. The terminal that connected to the green wire is the relay's ground, so just run a ground wire to any bolt on the fender well. I personally used the screw that holds the starter and battery junction block.I hope this helps!

 

I don't remember how the images went in the original post, it seems that the URL address must have changed. In any case, here you go:

 

I will say that this setup is extremely janky. I went back to the generator shortly after doing this mod. Now its just a backup that sits in the trunk that can be swapped in in a matter of 30 minutes. It would be a lot cleaner if you can score a 53 322 passenger side motor mount (they did not come with the generator mount) and go with a custom bracket or maybe a 401 bracket.

[Dobrini]

Hello, im new here.  I can’t se the pictures of your work, im about to do the same thing but almost no one in sweden have done this!

 

 

[Beemon]

On 4/25/2024 at 1:02 PM, Dobrini said:

Hello, im new here.  I can’t se the pictures of your work, im about to do the same thing but almost no one in sweden have done this!

 

 

Hi Dobrini, I had to dig for this one. All you really need to know is that it's a double pulley, you use the outside one, and a bunch of hardware store spacers. It's not the best, but it gets the job done. I rebuilt the generator and use it exclusively. This is now more of a backup, and I haven't really needed it. It's really ugly.