Greetings Crew Members. Hope you're having a great summer.

So dig this: Stopped at an intersection with everything ON- headlights, turn signal, brake lights, AM radio, windshield wipers and the cold Air blasting through the vents, my 1969 Chrysler Newport Custom AMP Gauge was way into the"no charge zone". The 46 year old "round back" alternator just wasn't doing the job.
I took it to an automotive electric shop for a rebuild and found out it was REALLY worn out inside. The guy did a beautiful job AND installed a slightly smaller diameter pully. More alternator RPM at idle means more juice and Man, can I tell the difference! Brighter lights everywhere, stronger turn signal cycling, just put the electrics on their tippy-toes.
Hope this helps anyone out there that may be a little "dim".

Regards, Capt. Boompy

 

Well that's fine for a cruiser than might not see a lot of high-RPM use. But here's the OTHER side of the coin

My first two Mopars were a 69 383 RR and then a 440-6 RR. The 70 had a couple of alternator failures. I once measured the crank pulley and the alternator pulley, and my (1970) recollection remembers a 4:1 ratio!!!! This means !!! that if the engine is shifted at 5000, THAT ALTERNATOR is spinning at TWENTY THOUSAND RPM!!!!

Someone "aftermarket" may or may not be making improved rotors and stators for the "roundback" alternators But the "usual" solution for use backyard guys is to use a "square back" to replace them. The squareback alternators have much more output because of internal design changes, at low RPM

 

Boompy -

You didn't bother mentioning what else was done to the car.
If the wiring is original or nearly so and if you are running a factory ammeter, those bright lights might be warning you of an impending problem.

See if you can figure out what kind of amperage, your alternator is now putting out. The factory ones were in the 60 to 65 amp range. The farther above that you go, the more of a fried wire risk you're taking. Since all cars are different and in different states of "upgrade", no way of telling what your safe range is.

Archer

 

The short answer is....read this article

http://www.madelectrical.com/electri...p-gauges.shtml

 

Thank you for your posts and that link, DDodger. I went back to the auto electric shop and ask the fella about the "other side of the coin". He assured me the new alternator bearings/guts could handle the slightly higher RPM. The new pulley is roughly 1/8th" smaller than stock.

Don't see myself twisting my 46 year old 383 to 5000+RPM, 4999 maybe.

Regards, Capt. Boompy

 

Thank you for your reply Archer. You also made some good points.

My car is what one would call a "time machine". Purchased from a little old lady, I'm the second owner. It's completely stock except for the MagnaFlow glass pack (actually it's packed with rock wool, not fiberglass) and a set of Hankook tires. The near perfect interior still has that Mopar smell.

If you could have seen the guts from my alternator before the rebuild, you would have wondered how it was supplying ANY voltage.

On the bench, my rebuilt alternator was putting-out around 55 amps. This is well within the limits the car wiring was designed for.
When it's "cold", the regulator is hitting the battery with about 13 volts. Once it's"warm", almost 14VDC. I have less than 1/2 volt drop between the alternator stud terminal and the battery. This speaks to the age of the wire and any corrosion.

The brighter lights are now probably closer to the stock lumins the original owner enjoyed back in the 1970s.

Stirred not shaken, Capt. Boompy

 

Boompy -

Was that 55 amps with the factory pulley or the under-drive?
You might be just fine. I hope so.
Even if you are getting "factory lumins", the wiring and ammeter are 46 years old. That's where the problems can creep up on you.

Archer