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1977 F100 - 460 from a 1969 Lincoln, C6 Trans, 9" Rear
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Discussion Starter · #1 ·
I've got a Motorcraft alternator installed, and can barely make out the last 4 digits printed on the case - 4025
1. I want to know how much amperage this alternator is currently able to produce
2. Is there a higher amperage unit that can bolt on? See pics below, they're not great but hopefully give you an idea of the setup.
3. If no higher amperage unit, is it possible to take the stock unit to an alternator rebuilder and have the amperage increased? I have a somewhat local rebuilder that I could probably ask, but I figure I'll drop the question here since I'm already making this post.

Reason for the upgrade - wanting to upgrade my e-fan setup. Currently have 2 80Watt fans. Also have standard lighting (halogen bulbs), 3 Summit Racing LED display gauges, and blower motor/heater. The fans I want to install are rated to go up to 49 amps, so I just didnt want to have an undersized alternator for the setup.
Based off of research from RockAuto, the standard alternator size is rated for 55 amps for a 1969 Lincoln 460 engine (Currently have that engine in my 77 F100).


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1977 F100 - 460 from a 1969 Lincoln, C6 Trans, 9" Rear
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Discussion Starter · #3 ·
Excellent, I figured that would be the case. Might try and pick a boneyard alternator and have it upped in amperage, then keep the original on the shelf in the garage as a backup.
 

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Go large cased 130 amp 3G, about the same size as that 1G(first generation) 55 amp +/- alternator with a lot more idle and total amperage.
 

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1977 F100 - 460 from a 1969 Lincoln, C6 Trans, 9" Rear
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Discussion Starter · #5 · (Edited)
Go large cased 130 amp 3G, about the same size as that 1G(first generation) 55 amp +/- alternator with a lot more idle and total amperage.
That’s awesome, thank you. I ended up looking this up easily and found something compatible. Obviously will require some electrical re-wiring, but this should be manageable.

Based off of the draws (30 amp heater, 50 amp fans, and the conglomerate of lesser items) I felt like 130 was a solid option.
 

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That’s awesome, thank you. I ended up looking this up easily and found something compatible. Obviously will require some electrical re-wiring, but this should be manageable.

Based off of the draws (30 amp heater, 50 amp fans, and the conglomerate of lesser items) I felt like 130 was a solid option.
Always glad to help if I can. The large case 130 amp 3G has around 80 amps of output at idle(around 2000 alternator shaft rpm) and tops out around 165 amps "full tilt". A '94 Taurus with 3.0 is clocked correctly for a 460 and fits the original alternator brackets(like a 70's Lincoln) and just needs a pivot spacer trim to bolt right up and be spaced correctly-but that depends on which V-belt pulley you choose.
 

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1977 F100 - 460 from a 1969 Lincoln, C6 Trans, 9" Rear
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Discussion Starter · #7 ·
-but that depends on which V-belt pulley you choose.
that was my next question. Also, would you use a specific wiring harness? Or just pull one from a junkyard?
 

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This should explain the wiring, the only wire used from your truck's original alternator/voltage regulator wiring is the Light Green/Red stripe wire, it sends "key on" 12V signal to trigger the alternator to start charging. You will be able to get rid of the wiring between the old alternator and voltage regulator. Not sure if you have an ammeter in your dash gauge cluster or not, that may require additional attention, but easily rectified.

Hope this helps.
 

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The G3 is a nice addition but there is 1 down side.The armature is heavy which can cause belt squeal on start up or when you punch it.This is with a single v belt.
 

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The G3 is a nice addition but there is 1 down side.The armature is heavy which can cause belt squeal on start up or when you punch it.This is with a single v belt.
Agree on the use of the V-belt, it is said at about the 100-110 amp mark the belt will slip depending on size of alternator pulley and width of belt. I solved this by modifying my original stock 460 3 belt sheeve crank pulley to accept a multi-rib pulley to drive the 3G multi-rib alternator pulley. Here's a pic:



 

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1977 F100 - 460 from a 1969 Lincoln, C6 Trans, 9" Rear
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Discussion Starter · #12 ·
Slick job on the crank pulley. I suppose I’ll run a VBelt for now once I do the conversion and see what happens. Worst case, I’ll modify the crank pulley to take a ribbed setup. You guys are one step ahead of me, clearly! Thanks for the diagram, I’m saving it now for reference. Likely going to do this conversion once hells furnace stops venting here.
 

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Slick job on the crank pulley. I suppose I’ll run a VBelt for now once I do the conversion and see what happens. Worst case, I’ll modify the crank pulley to take a ribbed setup. You guys are one step ahead of me, clearly! Thanks for the diagram, I’m saving it now for reference. Likely going to do this conversion once hells furnace stops venting here.
I didn't intend to make your alternator upgrade to be such a major undertaking, just tried to show what mods I've done to have a positive experience and not have pesky problems taint the outcome. I initially used a V-belt without much issue, but additional electrical loads required the needed modifications. They do make a replacement voltage regulator for the 3G alternators that delays the "turn on" timing of it, it's called load response control or LRC. If you have belt squeal at start-up, the use of a voltage regulator with LRC, will allow the engine to get up to speed without the additional loading of the alternator trying to charge the battery, there around a 2.5 second delay depending on model # and manufacturer. From what I understand this LRC VR also dampens the loading on the engine from say electrical fans kicking on. Hope this helps
 
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