6C Alternator Swap for 79-93 5.0

Hey guys, the ancient Lestek 120 AMP alternator in my '87 LX finally quit completely and I dropped in a 110A 6G out of an '04 3.8. Was a very easy, neat swap...correct pulley and regulator orientation, etc. The original 70A was useless, mine was the really poor early design with the sleeve bearings, it was only good for about 50A in real life and burned up several times before I switched to the Lestek.

For anyone with the slightly newer design (the one with the little black plastic fan guard), you probably haven't had the same problems. In my experience, those units were a lot more reliable.

Anyway. the 6G is humming along beautifully and there are plenty of them in boneyards, so they're cheap. Highly recommended for any early Fox owners out there who haven't already upgraded to the 3G or something similar. At 110A, they don't have enough oomph for any kind of killer sound system, but for an upgrade over the weak stock unit, they rock.

If anyone wants to do the swap and has questions or is looking for pics, let me know.

Carl

I'm not sure what year you're going from, but mine had the two-plug style harness.

One plug I cut off, bought a 6G harness (eBay, $11) and just matched the wires color-for-color. I could have also used the original 6G harness, because the boneyard was kind enough to include it.

The other plug carries two charging wires. I cut off that plug and connected both wires to a round terminal, which bolts up to the charging terminal on the 6G. Easy peasey.

Disclaimer: It's true that most of the posts I've seen (over at The Corral, for example) regarding the 130A 3G and similar swaps have talked about running new, heavier gauge wire to the battery. I didn't, and here's why:

1. I was too lazy;

2. I haven't made any changes that would increase the load on the battery or alternator, so there's no reason to believe that those wires will be carrying any more current than they are designed for, and;

3. When the factory alternator failed (and failed, and failed again), I replaced it with the Lestek, which was a reworked Delcotron rated at 120A. I ran it for almost 25 years that way, and when I took it out, the wires were fine...no sign of stiffness, blackening, scorched connectors, etc, and no continuity faults. I figured that was as good an endurance test as this particular vehicle was ever likely to see.

I'm guessing that reason #2 is probably the big one. If your original alternator is putting out its full rated output, but still draining the battery because you've got amplifiers or multiple driving lights or something, you should probably run a new charge wire, it's not hard to do.

In my case, I had the original alternator bench tested, it was only putting out 50A max and couldn't keep up. Also, it was a poor, failure-prone design. I upgraded to the Lestek at the recommendation of a good, old-timey starter and alternator rebuilder (he's still in business too!). I probably could have retrofitted a better Ford unit from a truck or whatever, but forums like this didn't really exist back then, so the info from other Mustang owners just wasn't out there.

If you plan to do the swap I can pass on a couple of fitment tips.

YMMV! Carl

This was actually a very straightforward swap. I didn't take any "before" pics, because I was removing the Lestek alternator which looked a little wonky in there, being essentially a GM product and all.

The first step was to remove the alternator. I did a test fit of the 6G and found two very minor issues. The lower mount uses a tapered sleeve to keep tension on the mounting bolt. That sleeve was a tad too long for the new alternator. It stuck out about 3/16" or so and I was concerned that I wouldn't have a snug fit when I was done without overtorquing the bolt and/or crushing the sleeve. I tapped the sleeve out with a drift and cut about 3/16" off of the narrow end. Here's a pic with the old alternator removed and the sleeve partially removed: http://www.flickr.com/photos/45687285@N02/8517371944/in/photostream

Next I had to root around for a bolt for the top mount. The mounting tab on the original alternator was threaded, the new one isn't, so I just popped in a bolt with a fiber washer for a snug fit. Here's a close up of the top mount with the 6G installed:
http://www.flickr.com/photos/45687285@N02/8517375336/in/photostream

For the plug you'll need, just search eBay for "6G alternator plug", if one didn't come with your new alternator. Cut off the original plug and match the green to green, and yellow to yellow. The black/white stripe wire isn't used, just isolate it. For my purposes, I cut off the second plug with the two orange/black wires attached, and ran them both to one heavy-duty ring terminal, which I bolted on to the 6G. To clean up the engine bay just a bit and give the wiring some protection, I used a wire loom and zipties. Here's what it looks like from above:
http://www.flickr.com/photos/45687285@N02/8517378222/in/photostream

Here's what the final result looked like, rusty junkyard pulley and all:
http://www.flickr.com/photos/45687285@N02/8516262257/in/photostream/

That's it! I just popped the belt back on and fired 'er up. 14.25 volts at idle and no issues so far. Again, if you're considering this swap because you've added a lot of power-hungry accessories, you'll probably want to run a beefier wire to your battery in place of the two stock wires.

Hope this helps! Carl

There are dozens of posts on other sites about the relative merits of each. If you Google "3g 6g alternator" you'll see what I mean.

I chose the 6G for ease of installation...no grinding of the bracket needed, and no stator wire to deal with. Supposedly they run cooler as well, but I'm sure the 3G would also be a worthwhile upgrade. If I'd had one laying around I'd probably have used that and just dealt with the installation hassle.

Here's a great post that goes a long way towards dispelling a lot of the 3G/6G misinformation out there: http://forums.vintage-mustang.com/v...or-conversion-testing-waters.html#post3942407