RustX7

This isn't pretty but it totally works.

The FD alt I had in my S4 TII bit the dust after a road trip last summer and I was in no mood to buy a new one for $130 or whatever it is only to have the POS burn out on me in a year, so I read around about the GM swaps people have done. I borrowed a junk one from an alternator shop and brought it home to size things up. I was thinking I'd have to cut off and grind down the mounting point in order to make it fit, but then it occurred to me that I might be able to just flip the darn thing upside down and use the adjuster arm point as the mount and attach the pivot arm to the thicker mounting point. Yes, the bolt hole for the pivot arm is rather small, but it's worked fine for me for a year of fairly regular 200 mile trips, and I wasn't comfortable drilling it out and having less of the alternator frame material to support it, or with paying a machinist $40 to drill a hole.

There are a few issues to overcome:

1) With the smaller bolt being used as the mount, it still has to go through the thicker bolt hole on the block. I struggled for a while trying to make a spacer out of a plumbing nipple but then I figured out it was way easier to just wrap the bolt in a few layers of aluminum from a cut up soda can. It likes to telescope on you a bit during installation but wiggling it around a little solves that.

2) The small adjuster arm bolt hole on the alt (now the main mount point) is threaded. You would think that this presents no problem as you can just insert the bolt from the other end (the end nearer the top of the engine) and go through the block hole and screw into those threads, but no, you can't fit a bolt that long back there. The solution to this is to use a stud rather than a bolt and screw it into the alt first, do your soda can wrap, stick it through the block and then slap a nut and some washers on the back. The stud I used came from somewhere on the intake (I think) of a different rotary (an S4 NA).

3) The post on the back needs to be moved to the other side of the alt or it won't fit on the engine right. Have the alternator shop where you get your GM alternator flip the back panel around for you. Unfortunately this is where you kind of have to visit an alternator shop unless you feel comfortable opening up the alternator yourself and messing with it. (The guys at the shop near me gave me my rebuilt GM alt for $80 including the back part being flipped and the pulley swap.)

4) Obviously you need the V-belt pulley instead of the serpentine that's on the GM alts normally.

5) Since the mount is now a smaller bolt it isn't perfect and the adjuster arm part of it needs to be secured better. Mine is ghetto right now with just another bolt and nut below it for the actual adjuster bolt and nut and alt to sit on. This has been working fine. I did have to tighten both the mount and the adjuster after the first several drives but it eventually hardened up and seems to stay tight now. Just make sure you tighten it really well every time.

I'm attaching pics, hope they show up okay. My camera sucks too I'm afraid.

Oh yeah, forgot to say that I'm pretty sure this alt is from an early 90s Buick. I imagine this method would work for a lot of similarly shaped alternators though so it may not really matter. Also it's just a one wire setup and they told me which wire to do what with at the shop. There are other wires on the alt but only one is necessary on the S4 (can't say for other cars for sure.) I think they told me that it put out around 100 amps, but all I know is its way better than the FD alt ever was, and unlike Mitsubishi alts it isn't known for dying easily.