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Old 11-30-2020, 08:09 PM   #1
russcc
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Default 30 amp generator vs 55 amp

The 21AS - 1000B generator is rated at 30 Amps, while the 21AS-1000-D is rated a 55 amps, both for 42-48, 8 cylinder pass. according to the green bible. How do you get 25 more amps or about 80% more amps out one generator, What is the electrical difference ?
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Old 11-30-2020, 10:11 PM   #2
Ross F-1
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Default Re: 30 amp generator vs 55 amp

Can't say for certain on that old of a car, but in 48-52 trucks it's a larger generator.
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Old 11-30-2020, 10:14 PM   #3
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Default Re: 30 amp generator vs 55 amp

They have different armatures and field windings, one has two brushes and the other has four.
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Old 11-30-2020, 10:15 PM   #4
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Default Re: 30 amp generator vs 55 amp

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The 21AS - 1000B generator is rated at 30 Amps, while the 21AS-1000-D is rated a 55 amps, both for 42-48, 8 cylinder pass. according to the green bible. How do you get 25 more amps or about 80% more amps out one generator, What is the electrical difference ?
I'm with Ross on this one. There was a "heavy duty" generator offered in 1940. It was primarily for police cars with a radio, extra lights, etc.

I have searched for one of those for decades but have never seen one.
The difference? As Ross had stated, it was larger than the stock generator. Not larger in diameter but rather, in length.
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Old 11-30-2020, 11:22 PM   #5
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Default Re: 30 amp generator vs 55 amp

i have a couple long ones, military surplus from the big one, ww2. sadly, they will not fit a stock single carb manifold as they hit the carb.
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Old 11-30-2020, 11:28 PM   #6
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Default Re: 30 amp generator vs 55 amp

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You would also require a voltage regulator to match that 55 amp generator. Most regs are rated at approx 32 amps. Regards, Kevin.
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Old 12-01-2020, 06:31 AM   #7
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Default Re: 30 amp generator vs 55 amp

Ford made a 51AS-10505-A regulator rated at 40-45 Amps for the 55 amp generator. Too scarce, and too long though, but great information. Thank you.
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Old 12-01-2020, 11:21 AM   #8
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Default Re: 30 amp generator vs 55 amp

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i have a couple long ones, military surplus from the big one, ww2. sadly, they will not fit a stock single carb manifold as they hit the carb.
Just curious, if they will not fit a single carb manifold, how do they mount them? Perhaps an offset mount over the head, like aftermarket? Maybe the 55 AMP generators being referenced are not for flatheads?
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Old 12-01-2020, 02:06 PM   #9
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Default Re: 30 amp generator vs 55 amp

The 1938 truck sales lit. Mentions an optional 12 volt system.
They mentioned something about fleets that use radio communication.
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Old 12-01-2020, 02:48 PM   #10
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Default Re: 30 amp generator vs 55 amp

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Just curious, if they will not fit a single carb manifold, how do they mount them? Perhaps an offset mount over the head, like aftermarket? Maybe the 55 AMP generators being referenced are not for flatheads?
The "big" genny for '40 fit perfectly as per the photos I have of police vehicles so equipped back then. I can't speak for other years.
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Old 12-01-2020, 03:01 PM   #11
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Default Re: 30 amp generator vs 55 amp

here's a pic i had on file. i assume they had they're own manifold. perhaps T16, or bren carrier. i had two T16's years before i had these gennys, sorry, didnt pay attention to what was on them.
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Old 12-01-2020, 09:43 PM   #12
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Default Re: 30 amp generator vs 55 amp

I have seen special intake manifolds that move the carburetor back to clear the long generator.
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Old 12-01-2020, 09:53 PM   #13
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Default Re: 30 amp generator vs 55 amp

another thought that just occurred to me, perhaps my long gennys would fit on the big 337 (?) truck motors as they must be longer
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Old 12-01-2020, 10:51 PM   #14
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Default Re: 30 amp generator vs 55 amp

The 337 have the room for a longer generator, but used 8BA style strap hold down. The 337s I have use the typical 8BA sized generator too, but I have seen pictures of a 337 with a long generator.
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Old 12-02-2020, 12:09 AM   #15
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Default Re: 30 amp generator vs 55 amp

thanks for that info, so the real application for the long genny i have is still a mystery !
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Old 12-02-2020, 10:46 PM   #16
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Default Re: 30 amp generator vs 55 amp

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thanks for that info, so the real application for the long genny i have is still a mystery !

I remembered seeing an add for an old bus with a generator like yours. I found it again, 1939 Ford bus. Scroll down through the pictures, notice the carburetor is moved closer to the fuel pump to clear the generator: https://barnfinds.com/crackerbox-1939-ford-school-bus/
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Old 12-02-2020, 11:16 PM   #17
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Default Re: 30 amp generator vs 55 amp

mr 38 coupe, thanks for that!!! it sure looks like the same one. looks like the back of the genny is darn near to the center water outlets on the head. mystery solved. years ago before i knew they would not fit a standard manifold i sold one at a swap meet. that fellow was very excited, well at the time, perhaps not when he tried to use it! maybe he's a barner, and now needs to find a bus?
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Old 12-03-2020, 09:17 AM   #18
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Default Re: 30 amp generator vs 55 amp

Anyone know what the greatest output is, i.e. greater than 30amps, for a standard length generator is and the part numbers?
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