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Got amps? GM Alternators! (pics and part#'s added)


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84 replies to this topic

#1 RavenTBK

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Posted 01 November 2004 - 01:03 AM

Well, I've been doing an absolute ton of research on this. I've been searching for an alternator of at least 100A that would bolt up without having to do any fab work to make custom brackets or whatnot. I was also looking for a one wire alternator.. but my research has shown me that going to a true one wire setup isnt really the best idea.. two wire alts are the way to go. Besides.. it isnt that hard to wire one up the right way. Why do it halfassed?

Well, I havent found the holy grail, but I have found one that is damned close. Its a lage case 100A off of an early 80s GM product. I wont tell exactly what it is yet until I get it together and cranking out the amps.

I lucked out with the large case, as they are more stout and heavy duty than the small case alts.. and being such, they have the tendancy to last almost forever.

Only work that needs to be done is file off 1/16" of metal off one of the ears, flip the adjustment bracket left to right, and attach the larger belt. With not having to cut, weld, for fab up custom bracketry, this should be a great swap for just about everyone. And.. with only having to shave that tiny bit of aluminum off the ear, its something that can easily be done on the side of the road, or in the parts store parking lot if you ever need to replace a bad alternator. Oh yeah.. I've found that most parts stores carry the stator plug in the electric connectors section. No need to wait for a special order T plug or having to yank one off a parts car. :D

I plan on finishing the swap tomorrow, and taking pics.. hopefully giving something useful back to the USMB community that has given me so much. :)

#2 sregor13

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Posted 01 November 2004 - 01:52 AM

Careful, if this is relevant- I was told that Subaru Wiring Harness's can not handle that nuch Juice 60-7o AMPS max. I would like to know how this works out for you. I can rember what year they made the Upgrade to the harness but I don think it was until Late 90's Ealy 2000's. Let me know if wires start melting becasue I need more DC Myself. Thanks

#3 NorthWet

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Posted 01 November 2004 - 02:04 AM

...Well, I havent found the holy grail, but I have found one that is damned close. Its a lage case 100A off of an early 80s GM product. I wont tell exactly what it is yet until I get it together and cranking out the amps.

I lucked out with the large case, as they are more stout and heavy duty than the small case alts.. and being such, they have the tendancy to last almost forever...

I went through this on my Datsun a couple of decades ago... Oh, sorry, drifted off for a moment. I installed a 65A GM external-VR alt (instead of the orig 35-ishA), and they worked just fine with stock VR.

However, the alternators tended to destroy their front bearings, even to the point of the front-plate (bearing carrier, mount ears) ovaling around the bearing.

Moral: Larger case does not necessarily equate to longer life.

But I would like a GM alt on my sube... And wiring issues should be handled by running some heavier power wire.

#4 Turbone

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Posted 01 November 2004 - 02:25 AM

This mod has been done by several so far. It should have a write up and be in the USRM soon. Havent heard of anyone frying their wiring yet.

#5 singletrack

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Posted 01 November 2004 - 03:18 AM

I'd also be interested in this, I've got a 105A GM alternator (with a lifetime warranty!) here. Then I could run the 1200 watt inverter I've got. Ya know, in case I wanna take the microwave camping.:rolleyes:

Also, it'd be great if my interior lights didn't dim in rhtym with the flashers....

#6 VaporTrail

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Posted 01 November 2004 - 07:57 AM

lots of people have put on the XT6 alternator, which is rated at 90 amps, with no problems. (though they don't like mud much :) )

I think the xt6 alt swap is in the USRM..... (see link above)

#7 edrach

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Posted 01 November 2004 - 08:50 AM

Also, it'd be great if my interior lights didn't dim in rhtym with the flashers....

More likely a bad ground than low output from your alternator.

#8 RavenTBK

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Posted 01 November 2004 - 10:46 AM

I'm well aware that this swap has been done numerous times in the past with resounding success. Same with the XT6 alt swap.

The issues I came up with with regards to both of those is theres some decent fabrication required for both swaps. With all of the GM swaps I've read up on, there was a need to fab up a custom bracket or two to get it to mount correctly. Since I dont have the time, materials, or the tools to do it right, this route was out of the question.

With the XT6 alt swap, theres not as much fab work, but more grunt work with swapping pulleys and such. With me living in the southeast, finding an XT in the JYs, let alone an XT6 is a challenge. Yall would probably die if you saw how much they want for a reman one at the local parts place with them not being "popular" here. They also dont stand up to the elements as well as the EA series alts....which is well documented. With the BushBrat and me living in the Apalachicola National Forest with all those trails to play on... well.. mud, sand, water, and all those goodies are on the menu on a semi-regular basis. After such, the parts store comes back into play - having to special order these items. So I should pay out the rear, only to have to wait two weeks for it to arrive from the warehouse each time I blow it up? Nope. Although I'm a diehard Ford guy (and prefer a 200A Ford G3 alt), the GM swap is cheap, and easily had down in these parts. Posted Image

The goal of this was to find a high amp GM swap that would drop in with even less effort than the XT6 swap. No fabbing of spacers, custom brackets, cutting any of the Subaru stock harnesses, or having to swap pulleys. With only a tiny big of filing, its literally plug and play.

With the issue of the stock harness not being able to handle more than 70A, well, that doesnt apply all too much. If you need the output, then logically you'd enlarge the "tube" the extra power must go through. Thats just common sense. Besides, the power curve of this alternator puts 70A at 4200 crank rpm (assuming a 2.5:1 ratio, stock GM). How often will you really be needing a full 70A of output? For those rare nights that you're on the trail, with your system cranked up full blast, highbeams and all the driving lights on, heater fan cranked cause its cold, while you're running the winch trying to get yourself unstuck? And even then, for how long of a duration will you be needing the full 70A? 45secs at the most? Please. Odds are you will never need the full power except for those short bursts, or jumpstarting another vehicle.

This is a cheap, easily had swap that can deliver the power when its needed, rather than overtaxing the alternator, pulling reserves from the battery, and leaving you with a fried alternator, and dead battery.

My reasons for the swap is when I kick my lights on high beam, I'm already pulling 490 watts, or 40.8 amps, which leaves a mere 15A of output left..but wait, that 15A only exists at full throttle. At cruise, the max output *is* 40A, leaving 0. Thats before you figure in the draw from the radiator fans, blower motor, stereo, and the rest of the system.. (taillights, markers, turn signals, etc).

Going this route delivers the extra headroom, if and when you need it.. without having to do any real fab or grunt work to make it happen. :D

Wow.. this has turned into a 9 chapter novel. I'm going to shutup and finish matching belts. Posted Image

#9 sandman

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Posted 01 November 2004 - 10:51 AM

It depends on where you are going to draw the current also. One way to protect your cars system is to run the charge wire strait to the battery and the car power rerun to the battery also. That way the main load will go strait to the battery and the car will use what it needs. You can then run your accessories off of the batttery post or something similar like that. Then your only concern would be the guage of wire from the back of the Alternator to the battery.

#10 NorthWet

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Posted 01 November 2004 - 12:28 PM

RavenTBK, good points about max rating vs. reality. Nothing likes running at max rating for long, so it makes sens to have something that is "loafing" under everyday situations. Things will run at 60-70% all aday long.

Sandman, just one word: Fusible links. :)

#11 Craven

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Posted 01 November 2004 - 01:31 PM

More likely a bad ground than low output from your alternator.

Or battery

#12 stansgl

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Posted 01 November 2004 - 05:22 PM

Please do post which alt it is when you get it in. I'd really like to upgrade myself. Thanks for all the great input also .. I'm learning alot listening to you all.

#13 RavenTBK

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Posted 01 November 2004 - 08:35 PM

Well, its in. I started around noon, and finished near 4.. but I only did about an hours worth of work in between. Too many distractions.. all the pretty college girls coming to pick up their cars.. bossman wanting me to fix his 4wheeler.. lunch.. etc etc. If I put it down, it would run about 45mins total. Easy swap.

The alternator was a drop in for the most part.. save the minor aluminum shaving, and playing musical belts.

I took a handful of pics... maybe 5 or 6. I'll apply them to the thread a bit later.

Afterwards, I had it load tested, and it throws 95A @ 4000rpm, and just over 40 at just off idle. This is adequate for my needs. I'll probably raise the idle slightly to take advantage of the 40A.. but thats later. I could also go with a smaller pulley on the alternator, but that would defeat the goal set out before of it being 99% drop in.

Like I said above, its a drop in for the most part.. but I can see you guys that have the stock aircleaner or A/C would have an issue. Its a big alternator.

Pics to come later. Work calls. :)

#14 Turbone

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Posted 01 November 2004 - 09:17 PM

Heres a link to previous discussions.
GM one wire conversion

#15 MorganM

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Posted 02 November 2004 - 09:34 AM

How about a part # for that bad boy? I know what I'm swaping in when this OEM alternator gives out :brow:

#16 cole098

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Posted 04 November 2004 - 12:04 PM

Bump it up....

#17 RavenTBK

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Posted 05 November 2004 - 10:35 PM

One of my drivers got thrown in jail, so I've been pulling doubles and sleeping in the middle. I had a lil bit of time before I get to run in again.. so I've uploaded the pics.

They're in my album, out of order, but there.
Clicky clicky!

Not all that much to see, as it was a pretty much drop in install.

Here's my list:
Alternator part number: P7157
Stock GM alternator plug
Belt 1.5" longer than stock (your mileage may vary.. I just happened to use 1.5")
Grinder/file to remove the bit of aluminum
About an hour's worth of time

Due to the large case design, those of you that have kept the stock aircleaner, or A/C might have fitment issues.

To wire it up was simple. On the EA T-plug, theres a large gauge wire, and a small gauge wire. What I did was connect spades to the GM plug, and connected the large to large, small to small. The stock harness connected to the B+ output. Eventually, I plan on rewiring the stock harness with some nice 10ga wire.. but thats not necessary at this time.

Here are the USMB threads I bookmarked for supplemental information:
Main Source: http://www.ultimates...read.php?t=8470
Extra Useless Info: http://www.ultimates...read.php?t=5324
Extra Useless Info: http://www.ultimates...ead.php?t=11742

So far, its been running for about a week without issues. :) I'll actually do a complete write up here soon. I will say this, the writeup wont be too much, as all "the work" was shaving that bit of aluminum off the ears. After that, it dropped in just like it was made for the Ru.

Enjoy.

#18 X35 Performance

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Posted 07 November 2004 - 01:16 AM

Think that'd work on a 86 XT Turbo EA82? It has the serpentine type belt, not a V-belt. Would the pulleys swap?

Looks like a good upgrade/replacement! Nice work.

#19 Huck369

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Posted 07 November 2004 - 07:50 AM

X35, I've been watching this thread too, wondering about fitment on the XT6, which has the Serpentine belt also....

#20 RavenTBK

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Posted 07 November 2004 - 09:07 AM

Since its a "generic" off the shelf GM alternator, theres no reason a serpentine pulley cant be put on. Now the EA pulley wont swap over, but I'm sure an alternator shop would have the proper pulley that would make it work.

The XT(6) is even more rare down these parts than EA81s are. Other than online, I've only seen two in person in my entire life. If I had access to one to see how it all looks inside, I could tell ya if it would just as easy of a drop in. But since XT6->EA alt swaps are common, theres no reason why it couldnt be made to work. At the same time, EA81 and EA82 alternators are interchangeable, so I do believe this could be applied to the EA82. However, I had the EA81 Brat/Wagon in mind when I was searching for the perfect drop in alternator. Only issue I can see some folks having is clearance issues due to the larger diameter case as compared to the stock alternator if theres A/C, stock aircleaner, or something else that could get in the way.

Good luck... I'll help where I can. Posted Image

#21 Mykeys Toy

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Posted 07 November 2004 - 12:16 PM

I am curious about the wire upgrade. How are you going to do it? If you upgrade from the alt to the harness, it is a waste of time since the factory harness abviously isn't going to take any large load. But, if you go to the battery from the alt it you'd have to tap power from the upgraded wires for the factory harness which would be a problem all in itself. Onto another thought.. if you have a large system or multiple off road lights and or air compressor (big current suckers) 10 Awg is not nearly sufficient.. If you even have plans to use something that will require 40-50 amps then i would go for at least 8 Awg which is good for 80-90 amps as long as the cable doen't exceed about 8'. 4Awg would be a big PITA but would provide the capacity to use lights stereo and a winch darn near simultaniously..


Mike

#22 RavenTBK

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Posted 08 November 2004 - 06:45 PM

With the wiring, currently I'm just plugged into the stock harness. I just havent popped in my high watt bulbs yet.

When I do get around to getting the high power stuff plugged in, I will do the same thing that I did on my Bronco with the 200A alternator. :D Either be lazy, and buy one of these from my good friend Ryan (http://fordfuelinjec.../index.php?p=67 bottom of page), or make something similar myself.

The output can go directly to the battery, and the harness can be stripped of its original current carrying wire. The only things that the alternator needs is the exciter wire, and that sense wire for the idiot light on the dash. The old current wire ran to the battery anyways..just took a long and winding road to get there.

The stock harness, if its in okay condition, can easily handle 70A.. so for most people, they should be able to plug and play without fear. And like I said before.. when are you really going to be running *all* of your accessories at once when you're on the trail? And even then, for how long? If you take a common sense approach to this upgrade, it will come out a lot cheaper, and be easier to get done.

Cheers.

#23 Snowman

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Posted 08 November 2004 - 07:48 PM

Wow! I always thought that getting a bigger alternator would be either a high-dollar or major fabrication affair, but this looks like a cakewalk! Definitely on my list of mods, probably not until next summer though. Thanks for all the great info.

#24 oddcomp

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Posted 09 November 2004 - 11:15 AM

tape off the factory sube charge wire
and then runa nice heavy one right to the battery

#25 RavenTBK

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Posted 19 December 2004 - 04:42 PM

Well, there was plenty of interest in this swap awhile ago. Has anybody else actually completed it yet?

So far, mines still doing great, with the stock harness, cause I'm a lazy bum. :cool:




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