77 J10 alternator upgrades

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Grand_Wag_85
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Joined: Sat Aug 27, 2011 8:46 am

77 J10 alternator upgrades

Post by Grand_Wag_85 » Wed Aug 19, 2020 7:47 pm

What good alternator upgrades are out there for the 70's trucks? Currently have the external regulated stock unit and it is dying a slow and painful death so perfect time to upgrade.
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

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tgreese
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Location: Medford MA USA

Re: 77 J10 alternator upgrades

Post by tgreese » Fri Aug 28, 2020 12:23 pm

Six days and no response?

A '77 should have the Motorcraft alternator. Not a terrible alternator, but the last year before the V8s went Delco. I'd think the easiest would be a Delco 10SI, which would require something different in the brackets.

The parts book shows the same drawing for both the Delcos and the Motorcraft, but the part numbers change. There should be plenty of bracket donors around if you wanted to use the proper factory parts, though I think the changes are minimal.

Wiring is simple. Delete the voltage regulator and wire it like a '78. I would also remove or bypass the ammeter if I went to a more powerful alternator. Then I would follow the diagram for a CJ (which uses a voltmeter).

Mad Electrical has a page about picking a 10SI or 12SI: http://www.madelectrical.com/electrical ... remy.shtml
The page makes a big deal about the clocking, but you can reclock these very easily. Take apart, use a toothpick to hold back the brushes, and reassemble clocked to where you want it.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green


RustyDusty
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Re: 77 J10 alternator upgrades

Post by RustyDusty » Mon Sep 07, 2020 2:49 pm

My 1990 also has the 12si, so ++ to that suggestion, and another source for brackets. Also, units can be found with 150 amps if you were going for future-proof.

I did not see a reference to one issue in the write up referenced by tgreese. The si alternators need a load of some kind on the #1 terminal. My Wag has a long brown wire that I suppose offers some resistance. Some write ups mention connecting a 194 bulb (that would have been an idiot light on an original GM install, or some write ups call for a diode to prevent feedback through that post.

Without the load on #1, the car might not want to shut off.
1990 Grand Wag
RB4/Holley 4160
A little rusty, and very dusty, but it makes me smile.

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tgreese
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Location: Medford MA USA

Re: 77 J10 alternator upgrades

Post by tgreese » Mon Sep 07, 2020 4:57 pm

A '78 will have a resistance wire in that location. That will provide enough voltage drop to shut off the engine. A bulb will work too.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green

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Grand_Wag_85
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Joined: Sat Aug 27, 2011 8:46 am

Re: 77 J10 alternator upgrades

Post by Grand_Wag_85 » Tue Sep 15, 2020 8:36 am

Thanks for the info! One thing I came across is the Ford 3G alternator. Can use my original brackets BUT they’re not exactly cheap.

Probably will do the idiot light as the wiring in this truck has definitely seen better days.
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

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