The Ford Barn

19Fordy · 01-31-2021, 06:38 PM

Would any harm be done if I installed an 8BA generator pulley on my alternator?
The alternator pulley pulley weighs 11 oz. Belt sheave dia. is 1 5/8 in.
The 8RT generator pulley weighs 18 oz. The belt sheave dia. is 2 in.

I just like the look of the 8RT pulley better but, if it will be detrimental to the alternator charging rate and put too much load on the alternator bearings , I won't make the change.

Also, don't want any chunks of metal shrapnel going though my hood and radiator due to a faulty steel pulley. Had that happen with a fan years ago.

Any thoughts welcome. Please excuse the tape.

V8COOPMAN · 01-31-2021, 07:24 PM

Quote:

Originally Posted by 19Fordy

Don't want any chunks of metal shrapnel going though my hood and radiator due to a faulty steel pulley. Had that happen with a fan years ago.

Any thoughts welcome. Please excuse the tape.

Hey Jim.....I really don't think the weight will make any dynamic, operational difference as far as the alternator handling the added weight.

I see the speed of the alternator being decreased by nearly 20%, and I see that as being detrimental POSSIBLY at idle, and with that depending on what your normal idle speed is. I'd THINK that if your idle is anywhere near 700 RPMs or more, you'll never know the difference. I suspect that most of your engine operating time is at a point well above idle anyway, so I wouldn't hesitate to give it a go. Just be forewarned....what the heck do I know? DD

PS.....I've had the pleasure of sending a couple of those little cooling ears found on a generator pulley up into the bottom side of a '56 Chevy hood, as well as a '34 Ford hood (a 283 Chevy buzzing over 6 grand can make that happen).

es

19Fordy · 01-31-2021, 07:30 PM

Thank you very much V-8 for your experience and insight.
You're making me think the standard alternator pulley will be just fine and dandy.

V8COOPMAN · 01-31-2021, 07:41 PM

Quote:

Originally Posted by 19Fordy

Thank you very much V-8 for your experience and insight.
You're making me think the standard alternator pulley will be just fine and dandy.

Jim....I was leaning toward the BIG pulley from the generator. DD

1948F-1Pickup · 01-31-2021, 08:29 PM

The previous owner on my truck slapped the generator pulley onto the Delco alternator when he swapped that into place. I haven’t had any issues over the past 5+ years with charging.

19Fordy · 01-31-2021, 08:31 PM

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1948F-1 Pickup: Thanks for the vote of confidence.

V8: You fooled me. I read you the wrong way but, still glad you replied.

Jack E/NJ · 01-31-2021, 09:01 PM

19Fordy>>>the standard alternator pulley will be just fine and dandy.>>>

Hmmm??? I thought you wanted the standard 8BA generator pulley to be fine and dandy. What am I missing here? Jack E/NJ

koates · 01-31-2021, 10:28 PM

Regardless of which size pulley you use you must still have the pulley fan fitted to cool the alternator otherwise it could overheat and pop diodes and burn out the stator with excessive temps inside the alternator. Regards, Kevin.

19Fordy · 01-31-2021, 11:17 PM

Jack, I want to use the 8RT pulley but am vacillating.

Koates: Your "heat" thinking makes sense also. A GM alternator cools by the little fan pulley vanes pulling "cooler" air into the rear of the alternator case. That's why the 12SI GM pulleys are better for cooling (then 10SI) because 12SI have larger openings in the rear case.

Trouble is the heat in the engine compartment of 40 Fords is already quite hot and not what I would call cool. Engine operates at about 180-195 degrees.

terry · 02-01-2021, 08:56 PM

About the heat, try it both ways and feel the alternator with your hand. I think about 10 miles with each pully would tell you a lot about whether the alternator is overheating. Terry

koates · 02-01-2021, 10:28 PM

Quote:

Originally Posted by terry

About the heat, try it both ways and feel the alternator with your hand. I think about 10 miles with each pully would tell you a lot about whether the alternator is overheating. Terry

Well the alternator temperature could vary a lot in regard to how many amps it had been charging at the time you place your hand on it. If it had been charging 50 or 60 amps for a period of time it would be quite hot but if it was charging 5 amps then it would be not hot. All depends on the state of charge of the battery or the number of loads turned on as to how many amps it is charging. Regards, Kevin.

cas3 · 02-02-2021, 01:50 AM

i agree with Kevin. normal start requires some amps, but a good battery with no load other than refilling after the start is just about runnin free. an alternator whines under load ,heavy charge, after starting, but should be quiet and not make any heat after 5 or 10 minutes. if you are familiar with you're vehicle, you may even notice a lower idle, and the "whine" when its working hard. more amps than Henry's generator, so its work for the motor to get back to full battery quickly, and not slowly like Henry liked. so...pulley size is rpm difference. too high of rpm would be a noise issue on early fords with the fan mounted genny, but not the case for you.

Charlie ny · 02-02-2021, 11:50 AM

19,
I'm running a 2 3/4" pulley on my GM alts '32 and '41 p'ups. I used Ford iron gen pulleys that happened to have identical threads. The pulleys originally supplied were

about 1 1/2"dia and spun the fan on the '32 into a buzz saw. No probs with charging at all and a quiet fan now. The pt# on the pulleys was 78- something, I believe for use on early 2 brush gens.
Charlie ny

01-31-2021, 07:30 PM	#3
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,923	Re: Generator Pulley fitting an Alternator Question Thank you very much V-8 for your experience and insight. You're making me think the standard alternator pulley will be just fine and dandy.

01-31-2021, 08:29 PM	#5
1948F-1Pickup Senior Member Join Date: Oct 2015 Location: Socal Posts: 795	Re: Generator Pulley fitting an Alternator Question The previous owner on my truck slapped the generator pulley onto the Delco alternator when he swapped that into place. I haven’t had any issues over the past 5+ years with charging.

01-31-2021, 08:31 PM	#6
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,923	Re: Generator Pulley fitting an Alternator Question Sponsored Links (Register now to hide all advertisements) 1948F-1 Pickup: Thanks for the vote of confidence. V8: You fooled me. I read you the wrong way but, still glad you replied.

01-31-2021, 09:01 PM	#7
Jack E/NJ Senior Member Join Date: May 2010 Posts: 2,173	Re: Generator Pulley fitting an Alternator Question 19Fordy>>>the standard alternator pulley will be just fine and dandy.>>> Hmmm??? I thought you wanted the standard 8BA generator pulley to be fine and dandy. What am I missing here? Jack E/NJ

01-31-2021, 10:28 PM	#8
koates Senior Member Join Date: May 2010 Location: Melbourne Australia. Posts: 2,078	Re: Generator Pulley fitting an Alternator Question Regardless of which size pulley you use you must still have the pulley fan fitted to cool the alternator otherwise it could overheat and pop diodes and burn out the stator with excessive temps inside the alternator. Regards, Kevin.

01-31-2021, 11:17 PM	#9
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,923	Re: Generator Pulley fitting an Alternator Question Jack, I want to use the 8RT pulley but am vacillating. Koates: Your "heat" thinking makes sense also. A GM alternator cools by the little fan pulley vanes pulling "cooler" air into the rear of the alternator case. That's why the 12SI GM pulleys are better for cooling (then 10SI) because 12SI have larger openings in the rear case. Trouble is the heat in the engine compartment of 40 Fords is already quite hot and not what I would call cool. Engine operates at about 180-195 degrees.

02-01-2021, 08:56 PM	#10
terry Senior Member Join Date: May 2010 Posts: 261	Re: Generator Pulley fitting an Alternator Question About the heat, try it both ways and feel the alternator with your hand. I think about 10 miles with each pully would tell you a lot about whether the alternator is overheating. Terry

02-02-2021, 01:50 AM	#12
cas3 Senior Member Join Date: Jan 2011 Location: sw minnesota Posts: 4,567	Re: Generator Pulley fitting an Alternator Question i agree with Kevin. normal start requires some amps, but a good battery with no load other than refilling after the start is just about runnin free. an alternator whines under load ,heavy charge, after starting, but should be quiet and not make any heat after 5 or 10 minutes. if you are familiar with you're vehicle, you may even notice a lower idle, and the "whine" when its working hard. more amps than Henry's generator, so its work for the motor to get back to full battery quickly, and not slowly like Henry liked. so...pulley size is rpm difference. too high of rpm would be a noise issue on early fords with the fan mounted genny, but not the case for you.

02-02-2021, 11:50 AM	#13
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: Generator Pulley fitting an Alternator Question 19, I'm running a 2 3/4" pulley on my GM alts '32 and '41 p'ups. I used Ford iron gen pulleys that happened to have identical threads. The pulleys originally supplied were about 1 1/2"dia and spun the fan on the '32 into a buzz saw. No probs with charging at all and a quiet fan now. The pt# on the pulleys was 78- something, I believe for use on early 2 brush gens. Charlie ny