Alternator mucking things up?
 

So the stock alternator died on my LS, which resulted in quite the annoyance as i must have jumped it about 5 times over 5 miles before realizing insurance would tow the damn thing for free. i swapped in the alternator from the other SA i had (1979), but it is a good deal bigger than the stock one (the big one has one mystery number on it, 14196, everything else is faded out. a quick google search confirmed that this one is in fact for rx7s). anyway, as soon as i put it on, and charged the car up, things got weird, and i started to lose hope.

while the car is charged and still connected to the jumper car, it turns on, and revs straight to 5000 rpm. if the tach drops below that, the car dies off. so we tried disconnecting the jumpers and starting it on it's own. same thing, but at 2000 rpm instead. a friend of mine suggested that the bigger alternator is too powerful or something to that effect, or perhaps i just hooked it up wrong (although i don't see how. there's two wires, and one's a simple screw on, the other's a clip connector)

when the previous alternator i suspect died (or was dying earlier that day), it start to lose power above 4000 rpm, which i attributed to the alt, but perhaps it's a symptom of something else.

as far as the car, everything is a bone stock (except the alternator of course) 1980 LS SA22C manual. i didn't have time yesterday to mess with the carb yet, so i'm hoping i might be able to do something there. carb was rebuilt a few months before i bought it, so it should be fine.

the weird thing is, it drove just fine the day before the alt decided to die. i had it idling at a steady (albeit kind of high) 1000 rpm, stayed strong through the powerband, etc.

Your problem is that the '79 alternator requires an external regulator. The '80 and on all had built-in voltage regulators. You can simply bolt in any 1st gen alternator ('80 and later) or an early 2nd gen alternator ('86-'88). You can do late 2nd gen alternators as well and even 3rd gen alternators, but they take a little more work.

Head down to the local junkyard and see if you can pickup something. Your best bet would be to get a '86-'88 2nd gen alternator (if from a TII, even better). These will have a greater charging capacity than your old alt and will bolt right up.

thanks, i was hoping this would be as simple as that and not a bigger underlying problem. is it possible to make a regulator circuit? i'm no stranger to the occasional jury rigged soldering job.

You could steal the regulator off the '79 and rig it up, but I wouldn't mess with it myself.

Used alts are a dime a dozen. If you don't have a nearby JY, post a WTB ad in the classifieds or hit ebay. You might even find someone close to you that would be willing to just give it to you (cleaning out garage, etc.).