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#2447810 - 02/06/18 10:06 PM Alternator differences
340clone Offline
mopar

Registered: 11/28/04
Posts: 446
I am looking to replace the alternator in my '74 Charger with a 440 to freshen up the engine compartment, and would like to keep it looking original. Car has factory A/C, tach and radio, and being a '74 it has electronic ignition. No other power options.

What would be the minimum amps advisable for these options, and also, how many amps would be recommended? Is the factory unit a 65 amp?

What year did the square-back come out? Was it '72?

If anyone could shed some light on which alternator should be used, it would be much appreciated!



Edited by 340clone (02/06/18 10:07 PM)

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#2447870 - 02/07/18 12:11 AM Re: Alternator differences [Re: 340clone]
RapidRobert Online   content
Circle Track

Registered: 11/20/03
Posts: 33130
Loc: Lincoln Nebraska
I'd get any mid 70's (squareback) alt at your parts house whatever is the highest amperage available right before the 78 amper came out for the 85 M bodies, that one has a thin stator & reportedly needs the common cheap chebby chrome swing arm (I ain't done it but I would work around needing that part) but you wanted OE for your year range. more important would be to clean ALL terminals/cables/connections from head to toe expecially in the alt sense circuit & clean the bulkhead & the batt to block/eng to firewall ground paths. grab your meter/check your voltage drops/charging rate. EDIT #1 caveat, don't use the alt to charge up a depleted batt & #2 if the system ever full fields for whatever reason (goes to max voltage) unplug the reg & drive home on just the battery & deal with it later & slo charge the batt back up on a charger.


Edited by RapidRobert (02/07/18 03:21 PM)
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#2447882 - 02/07/18 01:38 AM Re: Alternator differences [Re: 340clone]
Cab_Burge Online   content
I Win

Registered: 08/23/03
Posts: 30201
Loc: Bend,OR USA
I'm not sure if Mopar offered a hi output alternator for your car in 1974, having air conditioning stock it should have had a large output 65 amp alternator from the factory scope
When it comes to the running load ability of any alternator it will only put out the amps needed to keep the battery a certain voltage hence seeing battery read 13.+ volts at the battery when running with no load other than the ignition and the alternator charging the battery back up from starting the motor scope It shouldn't put out more than 14.5 volts when running after starting, I think shruggy
Your stock alternator should be fine as long as it puts out the amps it is design to put out work up
IHTHs thumbs


Edited by Cab_Burge (02/07/18 01:39 AM)
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#2447893 - 02/07/18 02:37 AM Re: Alternator differences [Re: 340clone]
SomeCarGuy Offline
master

Registered: 02/02/03
Posts: 8256
Loc: Someplace you aren't
Power master has a stock looking one that will light up a City block with its 95 amps. I don’t think you need that one or the wiring upgrade you’d need to do, but just throwing that out there.
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#2447947 - 02/07/18 09:15 AM Re: Alternator differences [Re: 340clone]
340clone Offline
mopar

Registered: 11/28/04
Posts: 446
Thanks for all of the great info! I was also looking into a 78 amp, but everything I'm hearing seems like it may be too much on the car's current electrical system.

I have looked at some of the 60 amp units in person at local parts houses, and some of them have the thin stator, with late 70's to early 80's dates on them. I wonder if they are really 60 amps?

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#2447964 - 02/07/18 09:39 AM Re: Alternator differences [Re: 340clone]
a12rag Offline
top fuel

Registered: 04/23/07
Posts: 1959
Loc: Calgary, Alberta Canada
Look for a mid 80's 5th Avenue unit . . . it will be a 78amp unit. The Alternator will only put out what your system draw is . . .

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#2447965 - 02/07/18 09:40 AM Re: Alternator differences [Re: 340clone]
Andrewh Online   content
master

Registered: 02/17/03
Posts: 7661
2 things, think of it as a straw your electrical system pulls from. not a hose pushing power into it.
as said above your electrical system will only draw what it needs.

can you burn something up? Yes you can, but you could have anyway.
The amps charging the battery if it were dead would be worst case other than a dead short.
if you run the amp meter bypass for charging you should be able to eliminate that issue and still keep a stock look.

second, you are probably right, if you check the parts house numbers they all probably are the same from when the square backs started to the late 80's.
I usually look for an 83 new yorker or mid 80's m body.
but find that the part number is the same all they way back to the mid 70's.
they don't need to carry 3 different alternators when 1 will bolt in and no one is going to complain about having too much power.

give it a try online and you will see the part number doesn't change.

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#2448000 - 02/07/18 11:04 AM Re: Alternator differences [Re: a12rag]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 4915
Loc: Caracas, Venezuela, SouthAmeri...
Originally Posted By a12rag
Look for a mid 80's 5th Avenue unit . . . it will be a 78amp unit. The Alternator will only put out what your system draw is . . .


up

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#2448004 - 02/07/18 11:10 AM Re: Alternator differences [Re: 340clone]
Moparteacher Offline
enthusiast

Registered: 07/02/08
Posts: 343
Loc: Boise
You could have an alternator capable of producing 10000 amps mounted on the car and it will still only produce/use what the car needs.

The amount of current/amps produced is dependent on the voltage level, and the voltage regulator takes care of that, and the resistance in the circuit.

As long as the voltage regulator works correctly and there are no short circuits, you have nothing to worry about running a larger alternator.

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#2448026 - 02/07/18 12:04 PM Re: Alternator differences [Re: 340clone]
crackedback Offline


Registered: 02/15/15
Posts: 1016
Loc: CA
Problem with most mopar alternators of the period is they SUCK regarding output at low/idle RPM. Make sure the idle speed output is sufficient.

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#2448125 - 02/07/18 03:24 PM Re: Alternator differences [Re: crackedback]
RapidRobert Online   content
Circle Track

Registered: 11/20/03
Posts: 33130
Loc: Lincoln Nebraska
^^^ yes there are 2 sizes of alt pulleys & you want the smaller one along with a std 7&1/4" crank pulley & a ~6" or so pump pulley for good coolant/fan (air) speed.
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#2448137 - 02/07/18 03:43 PM Re: Alternator differences [Re: a12rag]
John_Kunkel Offline
I Live Here

Registered: 01/20/03
Posts: 18999
Loc: Rio Linda, CA
Originally Posted By a12rag
The Alternator will only put out what your system draw is . . .


Another factor, often overlooked, is the rpm that the alternator produces its maximum output. Factory alternators are notorious for low output at lower rpm.

With the introduction of lower numeric axle ratios and more accessories, the alternator wouldn't keep up with the load at lower speeds. (the dim lights syndrome)
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#2448315 - 02/07/18 10:58 PM Re: Alternator differences [Re: 340clone]
SomeCarGuy Offline
master

Registered: 02/02/03
Posts: 8256
Loc: Someplace you aren't
Problem with just tossing a big alt on without adding a shunt is if you ever do end up for whatever reason drawing more amps than your harness can handle you’ll be in trouble. Like if you don’t remember to do so five years later and start adding stuff. Or the next owner, and so on.
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#2449307 - 02/09/18 08:13 PM Re: Alternator differences [Re: 340clone]
135sohc Offline
mopar

Registered: 02/19/12
Posts: 512
Loc: SoMd, USA
I did a Power Master unit on the old van (RIP) and would do it again if I was in the market for another one.

Idle output is better, it is not a Denso by any means but still vastly superior to the mystery junk in a box at the parts store.

Reliability as well was never an issue.

The rebuilders keep taking the same old worn out crap and just keep reusing it over and over again. keep cutting down the slip rings until there is nothing left. Mixing and not keeping the OEM matched stator and rotor together so the output is all over the place ect.

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#2449318 - 02/09/18 08:25 PM Re: Alternator differences [Re: 135sohc]
ahy Offline
master

Registered: 01/22/07
Posts: 7463
Loc: IN
If your current alternator is functional (sounds like it is) I would suggest just run it. Don't do anything to it.

As mentioned, parts house re-builds of 40 YO alternators leave a lot to be desired. An old alternator can only be freshened so many times and still work reliably.

A later squareback at 78 amps would have more output but do you need it? A Powermaster squareback would have even more amps and good chance it is reliable.

The weak link in the factory system is the connections. Bulkhead connector is top of the list. It overheats and melts. Ammeter conections next (if applicable) and small gauge factory wiring last on the list.

If you upgrade the alternator or even if you don't, suggest you use one of the many options to bypass and/or fix the weak spots in the OE system.

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#2449352 - 02/09/18 09:46 PM Re: Alternator differences [Re: ahy]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 4915
Loc: Caracas, Venezuela, SouthAmeri...
Originally Posted By ahy


A later squareback at 78 amps would have more output but do you need it? A Powermaster squareback would have even more amps and good chance it is reliable.



not because the 78 amps as max output, but the ~45 amps iddling these put out. but more, the better

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