Where to buy correct alternator for a 1969 340 swinger non a/c car

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dbphemi

dbphemi

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I need some advice on where to buy the correct alternator for my non a/c 340 swinger. The original alternator is long gone. I have a stock wiring harness and a new old stock 69 voltage regulator. It seems like most of the aftermarket and rebuilt alternators available are much higher amp rating than my stock one should be.
 
I like the way Rockauto's website works. Look it up by your application and all they have available wil be listed on the same page. I don't know the amp ratings for your car but it's probably a 46a. or there abouts. @Mattax can you help here?
 
toolmanmike said:
I like the way Rockauto's website works. Look it up by your application and all they have available wil be listed on the same page. I don't know the amp ratings for your car but it's probably a 46a. or there abouts. @Mattax can you help here?
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Rockauto has 55 and 60 amp alts . some of them say may not come with pulleys or may be square back.
 
My 70 is still a roundback. Let's see if we can find you one.
 
dbphemi said:
Rockauto has 55 and 60 amp alts . some of them say may not come with pulleys or may be square back.
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Lack of rebuildable cores is the problem. I don't see any roundbacks at Napa or O Reilly. None listed at Autozone either. Edit: I best look back at O Reilly. Rusty said they have some listed.
 
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i’d try to find a used one and have it rebuilt but it seems to be kinda hard to identify the amperage.
 
dbphemi said:
i’d try to find a used one and have it rebuilt but it seems to be kinda hard to identify the amperage.
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Should be able to tell by the part number. Do you have any electric motor shops that could rebuild it? I wonder if anyone here does them?
 
There is a shop in the Chicago area that @krazykuda has mentioned. I can dig that out. But you'll still need a decent core.

As we started to discuss in the "identify" thread, the amp ratings from Chrysler may or may not be the same as the ratings used by an aftermarket company.
Honestly most rebuilders haven't cared enough to pay attention to the combinations (rotor and stator) to keep the ratings correct, and ot get the best performance. That's been true for years.

There are two places that I am aware of that do close to 100% correct restoration. While I don't think that's what you are asking for, the photos are helpful in identifying alternators that haven't been molested, or at least not too badly.
This restored example from Plumcrazy has all the correct bits (externally anyways)
Approximately correct casting dates, presumbaly correct assembly date code.
 
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Functionally Important:
Correct stamped black alternator pulley.
The chromated machined ones don't seem to line up right and have too much interferance fit making them a PIA to remove.

Rotor that matches stator.
This is very difficult to get perfect because the stators are not easily identifiable unless its an unmolested alternator. The differences are in the number of of windings, size of wire, and maybe color of the insulating material or paint.

That said, the rotor's can be differentiated by measuring resistance or current draw. Any that draw significantly more than the shop manual allows are likley to cause problems wit the VR and the wiring over time.
To measure the resistance, remove the carbon brushes and place a probe on each slip ring.

Some rotors I've measured
NOS late 60s rotor: 3.7 Ohms
Rebuilt '70-71 alternator bought from junkyard 23 years ago: 3.5 ohms
In a very used 1973 'square back': 3.5 ohms
From the '73 FSM. Slip ring to slip ring the rotor resistance should be 3 to 4 ohms at room temperature.

In contrast, the rotor in a 10 year old Carquest 7024 square back measured 1.7 ohms! :(
Yes it may be capable of making more power. But its greatly increasing the load on the ignition and field circuit.
It drew 5.6 amps at 12.5 Volts when field current was tested on the car per FSM.
My experience that is about the maximum we should consider acceptable, and certainly not ideal with standard wiring.
It is higher than even the 1973 shop manual allows for squareback.
 
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See if you can get a used one that still has its original rear bearing. That would be a decent roll of the dice that it may have its original rotor and stator. Even if you need to get them rewound, you'll have the correct item for them to copy if you explain what and why you want it so.

Ideally you would want pulley 2444 478 and an alternator stamped 2642 944 or 2098 850 (which hopefully will have the pulley still installed).

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There's probably some other part numbers from earlier years that would also be OK.
 
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If by "correct" you mean physically similar, then what you want is a round back alternator with one field brush grounded. Pulleys can be changed, single/double. Parts on these have been changed so much over the years that the only way to really know it's output is to spin it up. If by "correct" you mean also correct part number, then you are in for a hell of a ride- I know.
 
A rebuild shop should be able to test the output at increasing rpm. However my experience is they rarely do this.
The Chrysler shop manual test is done on the car, with the engine at 1250 rpm, and voltage held at 15 V.
To compare with a bench test, the alternator rpm has to be converted to the engine rpm using the pulley ratio.
Also they need to test at 15 Volts, but that may be asking too much.
 
i don’t really care if it’s numbers correct , i just don’t want to burn up my wire harness or my voltage regulator. From what i’ve read on the forums the 60amp that’s available is pushing my luck on the stock harness. i’ve also read that some of the rebuilt alternators put out too high of voltage to the stock 69 and older regulators.
It’s a little confusing on figuring out how to identify the correct alternator. I kinda get the idea that finding an unmolested original is pretty rare nowadays.
 
Mattax said:
See if you can get a used one that still has its original rear bearing. That would be a decent roll of the dice that it may have its original rotor and stator. Even if you need to get them rewound, you'll have the correct item for them to copy if you explain what and why you want it so.

Ideally you would want pulley 2444 478 and an alternator stamped 2642 944 or 2098 850 (which hopefully will have the pulley still installed).

View attachment 1716120678

There's probably some other part numbers from earlier years that would also be OK.
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thank you this is very helpful!
 
dbphemi said:
i don’t really care if it’s numbers correct , i just don’t want to burn up my wire harness or my voltage regulator. From what i’ve read on the forums the 60amp that’s available is pushing my luck on the stock harness. i’ve also read that some of the rebuilt alternators put out too high of voltage to the stock 69 and older regulators.
It’s a little confusing on figuring out how to identify the correct alternator. I kinda get the idea that finding an unmolested original is pretty rare nowadays.
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Pushing your luck only if the system requires that much output. You could put a 120 amp alternator on a car and as long as it doesn't need 30-40 amps, that's all it will put out. With your car, turn the headlights on high beam, step on the brakes, wipers on high, and the blower on high and that will be all it ever needs.
 
toolmanmike said:
Pushing your luck only if the system requires that much output. You could put a 120 amp alternator on a car and as long as it doesn't need 30-40 amps, that's all it will put out. With your car, turn the headlights on high beam, step on the brakes, wipers on high, and the blower on high and that will be all it ever needs.
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True Mike. At least on the output side.
The trouble is on the feed to the rotor. The field current control only has three positions. On, Off and on through the resistors. The electronic version I think is the same.

So here's what happens.
Resistance of the rotor is 1.7 Ohms instead of 3.5 Ohms.
Power is supplied at the same voltage. lets say its 14 Volts.
Every time the regulator connects directly, the rotor draws power based on the 1.7 ohm windings.
Lower resistance results in more current as well as more power. That's how we end up with 6 to 7 amps flowing through the regulator and associated wiring.
It's only supposed to be drawing 2.75 Amps max at 12 volts. So maybe 3 amperes at 14 Volts.
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I could be wrong but seems like this is one of the issues with rebuilt alternators.
It fit with what I was observing when swapping alternators and noticed the revised squareback seemed to be the most difficult one for the regulator to control AND the one that was always involved with regulators failing. These were all transistorized versions of the points regulator. Several from Mopar performance, and Standard.

I think its also hard on the wiring. The A-bodies, at least these years, often got 16 and 18 gage ignition and field wiring.
'69 shop manual shows the wiring a little different than the other years and if so, then the wire to the regulator is 16 ga. which is a good thing.

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So the key switch connection, blue ignition wire, and connectors are only seeing around 5 to 6 amps at most.
The regulator and green 18 gage connecting wire are only seeing around 3 amps at most.

The fusible links in the regulator did not change in '69. I don't know their limit. My call to Standard Motor about the capability of their solid state version of that regulator failed to generate an answer. Their tech person only had the physical dimensions of the unit. :rolleyes:
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Its true the rotor that generates a stronger field should not need to be full fielded as long or as often as a weaker rotor.
But whenever current is flowing its going to be higher than factory planned on. How long/how many times can it do it that? I don't know. I do know I went through a lot of regulators when using alternators that had such rotors.
 
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That right there #16 should be a sticky! That and knowing how to use just a volt/ohm meter should be a requirement for membership here. :) ;-)
 
It's such a shame that cores are a problem these days. 10 years ago when I was retiring and selling off most of my inventory, I tried to find a core buyer for alternators and starters. Couldn't find a buyer anywhere close and shipping was too expensive for those in other states. I must have scrapped 60-70 alternators and about the same in starters. There were lots of original ones with date codes and correct pulleys.
 
I have a round back 1970 date coated one if needed PM me

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Anytime man I was reading earlier after I posted it that they changed after 69
 
It's more an issue of output. The later dual field alternators can be used on the earlier cars by grounding one of the field terminals
 
I thought the square backs are better at low rpm. Are they a direct replacement? (bracket wise)
 
Old Car Parts Northwest has shelves full of new old stock Chrysler alternators. You ought to be able to get whatever amperage rating you want, within a few amps. See here for detailed info on charging circuit upgrades. If you're actually driving this car, upgrading to a carefully-chosen electronic voltage regulator is a wise thing to do. There are several ways to do it; you can rework the alternator control (field) wiring to go to the '70-up regulator (Old Car Parts Northwest also has a good stock of NOS Chrysler ones), or you can keep your existing field wiring and use an electronic regulator designed as a drop-in for the old points type. As with everything else, they come in a range of quality; I prefer this one.
 
dbphemi said:
I need some advice on where to buy the correct alternator for my non a/c 340 swinger. The original alternator is long gone. I have a stock wiring harness and a new old stock 69 voltage regulator. It seems like most of the aftermarket and rebuilt alternators available are much higher amp rating than my stock one should be.
Click to expand...
Oreilly shows both single and double pulley round back 55 amp available.
 
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