Mach 1 Club

Our Classic Fords have the first generation of alternator (1G). The 2G and 3G alternators have the voltage regulator in the back of the alternator. You could remove the regulator and those 4 wires!
I was at the pick-apart yard and spotted a newly rebuilt 2G alternator, nice and clean, the tag says 75 amps. The only thing different about it is the pulley is for a flat serpentine belt. I brought it home, and changed the pulley with an impact. It is a direct fit , and it went right on to my 1973 Ford f-250. (We will get to the Mach 1 soon).
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The voltage regulator and the wiring came out. Now the headlights are brighter at idle. The 2G looks almost stock, the plug in connector is different, but is under the hose. But, the plug in connector can be a problem. They get dirty or corroded and heat up and can even start on fire. I have a new connector, and so far everything is cool.

For the Mach 1 , I wanted to try the 3G alternator. They come in 100 amp and 130 amp versions, they usually have a sticker, and the 130 amp has a bigger case. So back I go to the salvage yard, and get a 3G alternator. Changing the pulley had a small glitch. The 3G pulley is offset about 1/8 inch. What you need to do, is take your v-groove pulley, and put the lockwasher under the pulley, on the 3G. There it is, offset. Next, the adjustment arm that you use to tighten the belt needs to be about an inch longer, when using the larger case . I welded a bit of steel to the end and drilled a hole, easy. This is not a one wire alternator, you need to hook up 12 volt key-on, that went to the voltage regulator, and hook it to the green wire on the back of the alternator. The charge cable and yellow battery sense wire hook to your battery or starter solenoid.
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Nice. They work so much better than the older alternators and mechanical voltage regulators. Does the 2G work as well as the 3G? I installed the 100A (actually mine said 95A) 3G alternator in my 69 Mach 1. I went with the 95A 3G because Ford Racing use to sell a dynamically balanced version with the wiring harness and instructions. Balanced, not needed. But the kit made the change simple. With the 351W, early passenger side water pump inlet and pulley arrangement there were fewer modifications.

(1) I installed a slightly larger than stock diameter V-groove pulley from March with no modifications.

(2) I had to countersink one of the three screws that hold the alternator case together a little more. This was needed to clear the T-shape cast iron alternator pivot bracket that bolts to the cylinder head.

(3) Install the correct size metric bolt that attaches the alternator to the slot in the adjustment bracket.

(4) Make the necessary wiring changes.

(5) Last but not necessary, I installed a piece of fusible link wire in the charge wire since the original wire harness was only designed for about 60A. I don't know if that was wise. Later model cars use a much larger charge wire than these classic Mustangs. The thought was I'd rather ruin a fusible link then my wire harness if something goes wrong.

No more wondering if the charging system is going to work very well. I didn't need more capacity. I just wanted a better operating charging system.


Best Regards,
Mike

I did not install a fusible link, but it might be wise to have some circuit protection. I see a mega-fuse and holder at NAPA, that would work. The fit on a 351C is very easy. If you don't want to weld on the arm, you could just get a slightly shorter belt.

The 2G has more voltage at idle, no more dim headlights. For electric fans, a big stereo, or other power needs, you want the 3G. The 2G says 75 amp, tested-70 amps at 5000RPM. The 390 never gets 5000RPM, so it is like a 50 amp alternator, really.

I just used a Grade 8 bolt instead of the correct metric bolt. It works, you just need to tighten it with a back-up wrench.

It amazes me, having driven cars back when my 71 was new, and all cars had small amp alternators, my 71 was originally a 35 amp. With ac, power windows, and rear defogger, it would barely keep up with the load. I switched up to the 55 amp and was blown away by the difference. Now with the late model stuff we have access to, it's flat amazing how much difference there is between then and now. We were simply trapped by the technology of the day. I for one am glad for the improvements. Good to hear it was an easy swap. JTS 71 Mach1