Engine and Transmission Tech

tips, technology, tools and techniques related to vehicle driveline components

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MGBV8
Carl Floyd
Kingsport, TN
(4512 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Upgrading to a Modern Alternator
Posted by: MGBV8
Date: December 13, 2018 09:18AM

By Carl Heideman

[classicmotorsports.com]


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6469 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

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Re: Upgrading to a Modern Alternator
Posted by: BlownMGB-V8
Date: December 13, 2018 12:42PM

Note that with high capacity fuel pumps, radiator fans, upgraded headlights, stereo, and other electrical equipment even the 55 amp alternator may be a bit marginal.

Jim


MG four six eight
Bill Jacobson
Wa state
(324 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Upgrading to a Modern Alternator
Posted by: MG four six eight
Date: December 14, 2018 01:15AM

Yeah I would agree with what Jim said. If your running a carb, sometimes you can get away with a lower amperage unit.
With EFI and electric cooling fan(s), it's best to have at least 80 amps or more. Most newer vehicles are running 120 to 150 amp alternators due to all of the electronics.

Currently I'm running a 150 amp unit, mainly for the increased amperage output at idle. EFI and controllers like a stable voltage source, so by having "more then you need" amperage wise, it allows the fueling to be more consistent at lower RPM. The added bonus is that your cooling fan will run at it's maximum rated capacity as well!

Bill
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Moderator
Curtis Jacobson
Portland Oregon
(4577 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Upgrading to a Modern Alternator
Posted by: Moderator
Date: December 14, 2018 01:26AM

I chuckled at the term "modern". Those little Nippondenso alternators are great... but mine is over 30 years old already!


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6469 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Upgrading to a Modern Alternator
Posted by: BlownMGB-V8
Date: December 14, 2018 08:09AM

Bear in mind also, not all 80 amp alternators are equal. It does little good to install a 150 amp alternator that puts out 30 amps at idle. Granted that's an extreme example but not as far off the mark as you might think. A good example is the old venerable Delcotron. Originally a 63 amp unit, by changing the field winding they can go up to 100 or maybe even 120 amps. But to do that they lose capacity at slow speed, so in the end the 63 amp unit actually charges better around town.

Jim


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