I have a 79 f150 351m. got this alternator at a yardsale for 20.00. its a 577711 powermaster - can you guys look at it and see if it will retrofit to my engine.
I know the pulley has to be changed but im concerned about doing the wiring correctly. any helpful hints would be helpful. my truck has original alternator on it.

thanks

 

Looks like a 3G, so it probably will fit on there. I've put 3Gs in place of 2Gs, but never in place of a 1G like what our trucks came with.

And maybe someone can confirm that that is a larger >100 amp alt. I think it is - you can tell by the three casting ribs on the pulley side of the case, where each of them has two round holes. I think the smaller 3Gs have more holes in this spot? Something like that.

And now to hijack a monkey wrench into this thread: Could one remove or bypass the integral voltage regulator on the 3G, and instead use the old 1G external voltage regulator, and keep the ammeter working?

 

It will bolt right in, swap the pulley and you will need a 4ga charge cable with a 150 mega fuse. That's a self exciting regulator so no wiring really.

 

To answer the ammeter question, no. The ammeter doesn't work very well in these trucks fo it to matter. The stock wiring used a shunt that was not associated with the voltage regulator. The shunt is based on the stock charge cable which is dangerously undersized when doing a 3G swap.

 

I'd sure be interested in trying!
I just wonder if the one wire can simply be spliced to the new charge wire, and the other one spliced to the new sensing wire up at the alternator?
Or better yet, leave it on the original Yellow wire at the old regulator, and tap into that one for your 3G's sensing wire (the Red one in your pic) and see what that does.

It's true as it gets that these ****-poorly ammeters rarely work at all, much less tell you what you need to know, but after using the older ammeters for so long with great results, I've always wondered if the newer ones could be fixed.
And with a shunted type, you're not exactly worried about too much current frying the gauge and starting a fire under the dash, so it might be a fun experiment.

Or not...

Paul

 

looked up specs on it. looks to be 3g 200A. part 577711

 

I got to ask "Why use the old 60 amp? (maybe) regulator with a 100+ amp ALT"? You might as well leave the old ALT in place.

If you go to the 80-86 truck area FAQ and search out 3G ALT swap it has a lot of information from what ALT to use (for the 80-86 trucks) to what needs to be done for wiring.
BTW none of it list how to use the old 1G/2G regulator with the 3G ALT, you need to bypass the AMP gauge and go with a larger charge wire.

Now you can have the AMP gauge converted to volt meter, link I think is in the 80-86 FAQ 3G swap (rocket man), and you then have a good way to know if the charging system is working or not.
Dave ----

 

Hmmm. I wonder if there is an ammeter available, which is strong enough to handle the modern alternators. Then you could just stick its guts into an OEM ammeter. I like the idea of keeping the ammeter working.


Sorry for the hijack!!! But at least it is somewhat relevent material...

 

Okay that's the big boy, you will need a 250 maxi fuse and 2ga charge cable.

 

It was for one reason only, and that was to keep the ammeter in place and functioning. Which some people would like to keep.

Yes, the old Ford "inductive" ammeters such as those found in all '66 to '77 Broncos and (presumably?) other vehicles of the era would do it. But so should a shunted ammeter too. Anything that does not take the full current of the charging system through it's own wiring is pretty safe.
Even though the gauge face only reads up to 60a, it does not hurt them to run more through the wire as long as the wire itself can handle it. Since there is no direct connection to the gauge, there is no danger of a melt-down of the gauge itself. And as far as I know a shunted type is only taking a sample of the current flow and interpreting it on the dial. I would think the inductive type would be more accurate, but maybe that's a six-of-one, half-dozen-of-the-other kind of thing.

Now, the wire needed for a dash mounted inductive ammeter is another story. These are not shunted type gauges. It needs the full current running through the dash area and instrument cluster. Which, with a 100+ amp charging system would be tricky to do safely. Due to the length of the charge wire needed, the gauge of the wire would have to be in the 4ga or even the 2ga range. Or run large gauge for most of the run, then just 8ga for the short section under the dash. And it would also take pretty much re-wiring the basic layout in the cab so that the charge cable runs into the cab first, then back out to the battery.
So there again, you run into hassles that pretty much make it not worth the trouble to 99% of builders.

Dakota Digital makes a remote inductive digital ammeter though. I'm actually going to try one in fact. The inductive loop is mounted under the hood and the readout on the gauge takes it's signal from that. So I guess it's still a form of "shunted" ammeter, since it's not reading directly. But instead of a sample it's converting a digital signal into numbers on a gauge. Should have all the qualities of a safe gauge without running any big cables through the cab.
But depending on how your electrical system is set up, it would only read charge in positive amps. No way to read discharge, or negative amps on our trucks the way they're wired currently. Just the one wire between the alternator and battery for charge amps. Or between the starter relay and the cabin (Black w/yellow wire) for amps used.
So not as handy as a factory style, but at least it's safe and likely pretty accurate.

Paul