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Author Topic: Conversion from generator to alternator, 1940 La Salle  (Read 2912 times)

Offline John Barry [CLC17027]

  • Posts: 212
  • CLC Number: 17027
Conversion from generator to alternator, 1940 La Salle
« on: November 02, 2015, 01:58:32 PM »
I'm interested in the pros and cons of converting a 1940 La Salle from a generator to a 6 volt alternator with an external voltage regulator, with as much preservation of appearance as possible.  Let me stipulate that I don't intend the car to be judged regularly (trophies, etc., mean nearly zero to me) but what I do want is some measure of reliability while preserving appearance and functionality.  OK, I realize that there won't be some maintenance chores with an alternator that one must do with a generator (e.g., brush replacement) meaning that some functionality will be lost.  But you get the idea.

Please comment.
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Offline Andrew Trout

  • Posts: 232
  • CLC Number: 26976
  • Name: Andrew Trout
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #1 on: November 02, 2015, 02:40:51 PM »
If you're looking for an alternator but want to keep the appearance of a generator, you may want to consider an alternator that looks like a generator.



Rochester, NY
1961 Convertible

Offline John Barry [CLC17027]

  • Posts: 212
  • CLC Number: 17027
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #2 on: November 02, 2015, 03:00:39 PM »
I'd seen that just a few minutes after posting; that's a definite possibility.  Thanks.

Now I need folks to weigh in with the advantages and disadvantages also because I doubt this is an inexpensive move.
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Offline John Barry [CLC17027]

  • Posts: 212
  • CLC Number: 17027
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #3 on: November 02, 2015, 04:13:06 PM »
Fascinating.  One turn from a cold start, even after an extended period of sitting idle / unused?  And no dimming of headlights when idling?  How does one do that, especially the former?
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Offline kkarrer

  • Posts: 730
  • Name: Ken Karrer
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #4 on: November 02, 2015, 04:13:30 PM »
John,
    I've done this many times on Cadillacs (including my 41, 50, 55) and other early cars.  The expense depends in part upon whether you're converting a 6v or 12v system.  Yes, some folks want to convert a 12v system (just did that on a customer's 55 series 62 sedan) because they need more output for their AC system (some are dual as my last one was) and other newer systems.  Also, alternators aren't as problematic as generators are when it comes to the rear bushings (on GM) and the brushes.  The alternators are also much lighter.  I've used the PowerMaster and the PowerGen as they both give you the body of an original generator with the innards of a modern alternator with 65-75 amp output and no worries about the sometimes problematic external regulator.  Both of the previously mentioned alternators are "one wire" and have a built in regulator.  The cost of the most recent PowerMaster unit was under $400 and you need do nothing else if you're replacing a generator on a 53 and up Cadillac.  Converting to 12 on a pre 53 Cadillac (I've done two or three of these) is not much more expensive in terms of parts (bulbs and resistors), but it is quite a bit more labor as you have to replace the bulbs and coil and protect your radio, gauges and your heater fan.  An ammeter doesn't care about voltage (just switch the wires if it's originally a + ground system like 41 Cadillac) and neither will your starter, but your starter solenoid might be an issue especially if it's a 41 Cadillac.  That can be overcome by having it rebuilt.  There are many places that provide that service.  Ok, having said all of that I'm going to get some naysayers here because some guys just love those 6v positive ground systems and they're correct in that they work just fine when properly grounded and serviced, but if you need to jump start your car or someone else's you'd better hope there's another system like yours nearby or you're up a creek.  Also running AC on a 6V pos. ground system just isn't doable.  Of course I've noticed that quite a number of those same guys carry abound a spare generator in their trunk due to the aforementioned issues of bushings, bearings, and bruses (and sometimes the armature).  As to authenticity points, I've had my cars judged a number of times at GN with no point deductions.  It's not hard to dummy up the wiring and put the correct tag on the "generator."  By the way, some of these gen/alts are known as Genernators...if you're searching the internet.  I hope this is useful information.
Ken Karrer CenTex Reg.Dir.
1941 6227D
1955 convertible coupe
1956 Biarritz

Offline Dan LeBlanc

  • Posts: 4813
  • Name: Dan LeBlanc
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #5 on: November 02, 2015, 08:12:19 PM »
Art's 38 and 49 start very well. He is very correct about the importance of clean grounds and good connections. On the 49 especially,  the lights are very bright. His grounds are good and his in next ions have been cleaned up. Last fall, not so great. After cleanup,  very impressive.

One thing to note though,  the idle on the 49 is set slightly higher than the factory setting. Set your idle a little higher and you should be charging at all times like Art's car.
Dan LeBlanc
1977 Lincoln Continental Town Car

Offline bcroe

  • Posts: 3895
Conversion from generator to alternator, 1940 La Salle
« Reply #6 on: November 02, 2015, 08:20:09 PM »
A generator system can be made to work, including a 6V system.  I put a huge amount of miles
on them in the 60s.  You can expect to replace the brushes every 40,000 miles, and have some
problems with the mechanical regulator.  With stuff turned on you will get discharge (lights dim)
at slow idle. 

If you have more loads you might want an alternator.  That is a very simple thing using an
internally regulated 12V alternator, if 12V is needed.  Don't use a one wire alternator, as it
won't give the best regulation, and that will be even more important running 6V.  A 6V alt
works but isn't as efficient, because the losses in the rectifier diodes take a much larger
part of the generated output.  A conversion to an alternator that looks like a generator
will be an order of magnitude more expensive than the lowest cost (and more effective)
option.  Its your money.  A higher output alt may require some bigger wire, not so much
for a 12V conversion.  good luck, Bruce Roe

Offline John Barry [CLC17027]

  • Posts: 212
  • CLC Number: 17027
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #7 on: November 02, 2015, 09:39:11 PM »
Art's 38 and 49 start very well. He is very correct about the importance of clean grounds and good connections. On the 49 especially,  the lights are very bright. His grounds are good and his in next ions have been cleaned up. Last fall, not so great. After cleanup,  very impressive.

One thing to note though,  the idle on the 49 is set slightly higher than the factory setting. Set your idle a little higher and you should be charging at all times like Art's car.

The idle is simple to adjust.  Now: could you please define "clean grounds"?  Looks to me like it's a matter of going over each and every ground, perhaps applying emery cloth to yield bare metal, tightening everything, etc.
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Offline Dan LeBlanc

  • Posts: 4813
  • Name: Dan LeBlanc
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #8 on: November 03, 2015, 07:35:47 AM »
Art is correct.  The increased amount of power accessories necessitated the move to 12v.  Electric power windows, electric power seats, air conditioning - all heavy draw items.  In basic form, most cars were fine on 6v without power accessories.  I believe Ford and Mopar vehicles straggled on a bit after GM with 6 volt.  Buick went fully 12V in 1954 (1953 was mixed for Buick), Pontiac and Chevrolet in 1954, and Ford in 1955/56.  Chrysler was approximately 56 also.

If you think of things that were added to cars around this time, it will all make sense.

Dan LeBlanc
1977 Lincoln Continental Town Car

Offline Raymond919

  • Posts: 191
  • CLC Number: 26141
  • Name: Ray Schuman
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #9 on: November 03, 2015, 09:25:15 AM »
Art's 38 and 49 start very well. He is very correct about the importance of clean grounds and good connections. On the 49 especially,  the lights are very bright. His grounds are good and his in next ions have been cleaned up. Last fall, not so great. After cleanup,  very impressive.

One thing to note though,  the idle on the 49 is set slightly higher than the factory setting. Set your idle a little higher and you should be charging at all times like Art's car.

Hi, I have a '49 and found that I need to set the idle just a bit higher than the specs to have the ammeter pointing where I want under various situations. I think I have it around 425. My car is 6 volts and I'm very content with it.
Now, my stupid question. Please don't laugh. Why can't the generator pulley be changed with a very slightly smaller one so that it turns more when the car is set at the correct idle? This will give the generator more rpms while the engine rpm will not have to be set higher.
Ray Schuman
« Last Edit: November 03, 2015, 09:27:04 AM by Raymond919 »

Offline Dan LeBlanc

  • Posts: 4813
  • Name: Dan LeBlanc
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #10 on: November 03, 2015, 09:32:52 AM »
Actually, Ray.  I don't think that's a stupid idea at all.  It acutally makes perfect sense.
Dan LeBlanc
1977 Lincoln Continental Town Car

Offline bcroe

  • Posts: 3895
Conversion from generator to alternator, 1940 La Salle
« Reply #11 on: November 03, 2015, 09:49:04 AM »
Quote from: Raymond919
  Hi, I have a '49 and found that I need to set the idle just a bit higher than the specs to have the ammeter pointing where I want under various situations.

Why can't the generator pulley be changed with a very slightly smaller one so that it turns more when the car is set at the correct idle? This will give the generator more rpms while the engine rpm will not have to be set higher.    Ray Schuman 

If you were to check a lot of alternators, you would find that the pulley in fact does vary a lot
in dia.  Possibly the same pulleys would fit a generator (didn't check them).  The one
problem is, reducing the size means there will be more pull on the belt & less contact area,
increasing the chance of slipping.  This may be less of a problem on a low output gen, than
on a high output alt.  Bruce Roe
« Last Edit: November 03, 2015, 01:09:09 PM by bcroe »

Offline Dan LeBlanc

  • Posts: 4813
  • Name: Dan LeBlanc
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #12 on: November 03, 2015, 10:01:24 AM »
You would need to be sure to use the fan from the generator though.  Remember, generators draw air in from the rear, alternators from the front, so the fan blades are pitched differently.
Dan LeBlanc
1977 Lincoln Continental Town Car

Offline Dan LeBlanc

  • Posts: 4813
  • Name: Dan LeBlanc
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #13 on: November 03, 2015, 10:39:45 AM »
Yes, it worked well at the time, but what worked well then doesn't necessary apply today.

Art.  Remember the night before Hershey show and someone we know was stuck in traffic, at night, for over an hour, idling, with the lights on and fan blowing to keep the windshield clear in the rain and the glow of the GEN light in the dash reminding him he had to go into neutral and get the revs up or drain the battery completely.  Either way, the generator and voltage regulator crapped out after that episode.  Things like that did not happen when these cars were new.  You just drove.  No traffic jams on I-81 then.

So, yes, re-engineering, or tweaking the technology of the day is something we have to do today.
Dan LeBlanc
1977 Lincoln Continental Town Car

Offline Caddyholic

  • Posts: 505
  • 1961 Series 62 Convertible 1962 Coupe Deville
  • CLC Number: 29283
  • Name: Jim Lumma
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #14 on: November 03, 2015, 11:07:54 AM »
Not to hijack the thread but here are my thoughts.
1. I have done the gen to alt conversion on my 61 and have no regrets. (very simple a 61)

2. The industry change from 6-12v was also related to the need to cranking larger higher compression V8s.

3. I think the Pulley is  sized to the operational upper end of the engine rpm vers generator max rpm. (not to over rev the gen).

4. How did the factory determine the idle rpm? Does it have to done with transmission?   They designed it not to charge at idle?
I got myself a Cadillac but I can't afford the gasoline (AC/DC Down Payment Blues)

1961 Series 62 Convertible Coupe http://bit.ly/1RCYsVZ
1962 Coupe Deville

Offline bcroe

  • Posts: 3895
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #15 on: November 04, 2015, 01:46:47 PM »
My take on car electrical power.

I hear said that the old systems were engineered to work fine in their time.  The fact
that we stopped using them suggests maybe they had shortcomings after all.  Even
my lawn mower doesn't use a points ignition or a generator.  Why did we change? 

Someone first put a big battery in a car so it could starts itself.  This was driven by
safety, convenience, women drivers, and available technology.  Why they picked 6V
(3 lead acid cells in series) I don't know, but that was about the lower practical limit. 

Before long a lot of other equipment was added, all designed for 6V.  When radios
went into cars, the new electronics industry designed vacuum tubes with 6V heaters,
which became the dominant standard right through today.  Later tubes with 12V and
24V heaters were added for aircraft, and post war cars. 

Once a technology is well developed, there is the tendency not to change from
the "standard" until the need is overwhelming.  As cars added more equipment,
there was pressure to improve the 6V source.  The 12V alternator with internal
regulator was a huge step forward. 

Car alternators were made practical when the semiconductor industry (evolving from
the 1947 invention of the transistor) produced the required large, cheap rectifier
diodes.  These diodes lose about 2V of the generated power, so they are much
more efficient and doubly power capable in a 12V system, compared to a 6V.  An
alternator is much lighter, and easily out performs a generator.  It doesn't need
those radio interfering, short life, commutator & brushes.  The voltage regulator
may be self contained, another source of excessive wiring, radio interference, and
maintenance problems eliminated. 

The points ignition system worked on 6V, but it worked a lot better on 12V.  The
highest performance engines didn't even try to use either, they went to magnetos. 
The actual points seem to be the final limiting factor.  12V allowed faster coil
energy charge up (higher rpm & more cylinders), with better current limiting
(ballast resistor) over the rpm range, along with a short "boost" during starting
despite lowered battery voltage.  All that said, the issues of poor efficiency and
limited spark energy of points systems were not completely put to rest till
electronic ignitions came in.  Bruce Roe

Offline JoeCeretti

  • Posts: 146
  • Name: Joe Ceretti
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #16 on: November 04, 2015, 01:57:40 PM »
Changing the pulley out for a smaller one will allow the generator to charge at idle but will over spin it at full engine RPM's. If only that was a practical solution the electrical systems designers of the day would have done it. I remember reading somewhere about Delco working on a pulley system that would somehow vary depending upon RPM to solve the problem but it was abandoned when alternators became a viable option.
1938 60S nearly done and then destroyed by fire :(
1989 Buick Riviera (Arctic White Paint / Blue Cloth Interior)

Offline bcroe

  • Posts: 3895
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #17 on: November 04, 2015, 02:16:08 PM »
Changing the pulley out for a smaller one will allow the generator to charge at idle but will over spin it at full engine RPM's. If only that was a practical solution the electrical systems designers of the day would have done it. I remember reading somewhere about Delco working on a pulley system that would somehow vary depending upon RPM to solve the problem but it was abandoned when alternators became a viable option.

Yea, the alternator was an elegant solution.  I suspect they also have more rpm capability.  Bruce Roe

Offline bcroe

  • Posts: 3895
Conversion from generator to alternator, 1940 La Salle
« Reply #18 on: November 04, 2015, 07:10:10 PM »
Broe, in your first sentance you reaffirm.  In the times in which they were built. If nothing is added, then it still is in the time in which it was produced. My 38, 49 are still, as they were produced. More then adequate. Had my 49 out today. Had ran in 8-9 days. Two turns and it fired right up. Ok, i understand updating for some but my question us the same, why??? 

Its NOT me telling others they need to change.  I'm just discussing the options & benefits. 

I certainly will tell my own experiences.  I drove my 62 40,000 miles a year at considerable
speed, and usually with the lights on.  After having the generator go out every Thanksgiving,
I started a maintenance program with rebuilt spares.  But in the end I put in a 63 bracket and
an alternator, eventually upgraded to an internal regulator.  Less failures, no noise in my
HAM radio receiver.  I even converted to a double pulley alternator belt so a failure wouldn't
stop me.  I could tell similar stories about the points ignition and building 304 stainless steel
exhausts, because I'd rather be driving my car than fixing it. 

Feel free to keep your car in any condition you like.  I do the same, on the road.  Bruce Roe

Offline Art Gardner CLC 23021

  • Posts: 1605
  • Name: Art Gardner
Re: Conversion from generator to alternator, 1940 La Salle
« Reply #19 on: November 05, 2015, 10:12:40 AM »
6v works well, generators work well, points ignition work well.  All three of them were state of the art at the time.  However, technology advances over time and it is undeniable that 12v is more forgiving, alternators do a better job of keeping batteries charged and lights bright (mainly by providing higher power at low speed), electronic ignition is more reliable (well, certainly less maintenance).  Anyone who chooses to keep a car completely stock is well justified in doing so.  Anyone who chooses to update the electrics for one reason or another is well justified also.


If you want to switch to an alternator, I recommend the Powergen units (have used them several times).  They look exactly like the generators and mount up the same way (no special brackets needed).  So they look correct under the hood.  I just put a 6v unit in my 51.  Very nice unit.  They only downside is that these are costly ($400+)...
Art Gardner


1955 S60 Fleetwood sedan (now under resto)
1955 S62 Coupe (future show car? 2/3 done)
1949 S60 Fleetwood sedan (restored 30+ yrs ago)
1958 Eldo Seville (2/3 done)

 

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