Correct 3g alt

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Jan 21, 2021 | 03:21 PM

jrpitdog

Thread Starter

Cross-Country

Joined: Dec 2020

Posts: 51

Likes: 1

Correct 3g alt

89 f250 460. I want to do the 3g swap. I have read through several threads and I am getting mixed answers. So I want one of the 130 amp alts. Do I need the 7" or the 8.25" mounting? I have read people saying either??? I wont need any different brackets or anything correct?

Jan 21, 2021 | 05:56 PM

torq'ta 5 8

Lead Driver

Joined: Jan 2019

Posts: 5,083

Likes: 868

From: N.W. Alabama

measure yours, see link below (first post shows how)
3G Interchange Facts. If you're thinking 3G read here. | Bronco Forum - Full Size Ford Bronco Forum

Jan 22, 2021 | 05:43 PM

aquartlow

Mountain Pass

Joined: May 2006

Posts: 194

Likes: 31

From: Summerfield

FWIW, I use the 7" pivot mount version on my 472(DOVE 460 based block) in my '79 Ranchero, fits perfect, not sure why they say in the Bronco article to use a 8.25" version, the 7" looks and works as it should. I also use the large cased 130 amp 3G sourced from a '94 Taurus w/ 3.0 due to the alternator's "clocking" being correct for a 460. Lester # 7765. I can tell you a 130 amp alternator and a V belt will give you belt squeal if you need full amperage at just above idle(like using a winch), stick with the 6 rib serpentine pulley if possible(I believe a '91 has serpentine belts) or to get the belt to stop squealing may require a belt that will end up over tightened, putting too much pressure on the alternator's front bearing. The 7" pivot mount large case 3G is just about a direct replacement(read about the same size) as a 55-65 amp 1G or 65-75 amp 2G alternator. Hope this helps. Here is what I am working with: