I have a 1970 cuda 340 with a pertronix unit in distributor. I had a newer square back alternator on car with no problems. I switched it to the correct round back alternator and while idleing the ground wire to the alt meter got hot and started smoking(ralley dash) alternator is of unknown condition but looks new and rebuilt. Sounds like something i read here before but can't find it.

are you sayin one of the ammeter terminals in the ralley dash was loose & started smoking from the poor/loose connection right there? More info please

It was tight but it did get hot and started smoking. The two wires that go to the gauge heavy gauge red and black wires. Black one got hot.I didnt test anything just unplugged wires from alternator.

Poor connection/heat/failure at the ammeter studs is a fairly common problem... may not be the alternator. Suggest you remove the ammeter connections, clean well with emery cloth, tighten well and re-connect.

Fire it up with the alternator hooked up and check voltage at the battery. At ~2000 RPM with accessories turned off should be between 13 and 14.5 volts. If voltage is OK alternator is OK.

If voltage is high, there could be a short in the alternator (aka full fielding) or problem with the VR and wiring.

so I have to ask, and maybe it is a dumb question, but did you change the voltage reg when you changed it back to the round back?

and is it a stock round back or a high out put?

Not trying to be a WA but there is no 'ground' on an ammeter. An ammeter is in series so both terminals are above ground.

What I would do is (1) take off the positive batt cable from its batt post. (2) take off the heavy red/black wires/ring terminals from the ammeter studs in the ralley dash and connect them all securely together to each other with a small bolt/nut thru the ring terminals. (3) back at the battery (with everything in the car shut off incl ign) see if you have any amperage draw on your meter in series between the batt positive cable and the batt positive post (meter on low amps scale). If NO draw (eng off), hook the cable back onto the post & then start it up with the ign key with your nose under the dash to immed check for continued smoking & shut it off if any smoking anywhere. if not smoking the (now isolated) ammeter/stud connections is the prob. If there IS a draw, dont start it up but dig in & find/fix the source of the improper draw first then see if the ammeter or elsewhere is bad (smoking).

Thanks for the suggestions i will try to fix it this weekend. The reason i assumed it was alternator related was it was fine with one alternator then after changing it with a unknown new to me alternator it smoked. I will check the loose stud first then go after the full field. thanks for the help ill let you know how it turns out.

If you had a 35 amp alternator origninally and swapped in a 65 amp or bigger you may have ended up overloading the wires, Mopars are horrible on the bulkead and amp meter connection getting loose and corroded Good luck, let us know what you do and decide how to fix it