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Thread: 10si alternator rebuild

  1. #1
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    Default 10si alternator rebuild



    At one time for about 30 years, the Delco 10si was the most common alternator around - and its slightly improved, larger output cousin the 12si....I run these on both my 70cj5 and the 58 willys with sbc....the one on the cj was working fine in terms of electrical output, but started making a growling noise on the way back from Holy Cross a couple months ago - basically a bearing was going bad, and it only got worse on the next couple runs....These rebuilt NAPA/Carquest etc units are pretty cheap, but I had done some work to the housing sleeve to help stabilize the mount, and figured it was worth an attempt to replace.....Most likely it was the wobbly mount that lead to the bearing wear....

    This summer I put in a sleeve on the bottom bolt/pivot - I think when they 'refresh' these housings, they are over enlarging the mount hole as the one on the sbc is the same - I tried just swapping it out at first. In this case, I drilled out the hole just a bit, and put in a sleeve that fits the mounting bolt perfectly, and used a touch of epoxy to hold things in place. That solved the wobble problem, but I think the bearing damage was already done and it didn't take but a couple months for it to start growling.


    When you separate the two halves, the back half has the stator ring (wire coils - not pictured here, but is below) as well as the rectifier (rectangular finned thingy that changes alternating current to DC) as well as the dual plastic housing for the spring loaded brushes and the internal voltage regulator (this is a 3-wire unit), the diode trio, as well as a needle bearing cap that sits in the back of the housing....this is one of the two bearings to be replaced. You can also see the brushes are pushed out by the springs when the rotor is removed....


    Here are the brushes up close (and the voltage regulator underneath and the diode trio on top):


    One of the brushes in particular was worn significantly more than the other - usually that means a bad spring, but in this case its just kind of weird....but you can remove the brush with its metal clip and replace:


    The other front half holds the pulley, fan, front drive bearing and shaft along with the rotor that spins inside the stator coils - sorry no pic....but here is the back half with new needle bearing installed, the new front drive bearing, and the brush housing....a paperclip or pin can be used to hold the brushes back against the springs until everything is installed.


    Reassembly of the back half with new needle bearing in the bottom, new brushes, and stator ring in place:


    I put the front half in the oven for 10 min with the bearing in the freezer so it slipped right in - no need to have to pound it in....


    Assemble the two halves of the case back together...and you can see the pin that holds the brushes in has a hole through the back of the case that can be removed (pulled out) as the last step allowing the brushes to push against the rotor....


    Sorry I didn't get pics of the front halve with the drive bearing and rotor - I wasn't really thinking about a full write-up - but its pretty straight forward. The front case half has a bearing in the front opening that the rotor shaft goes through, the fan and pully slide on the outside end of the shaft, and then you tighten it down with nut...
    ___________
    James Orofino
    1970 CJ5
    1958 Willys Wagon
    2010 Tacoma TRD

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    Default Re: 10si alternator rebuild



    Nice work.

    My eye catches one item you have commented upon with respect to your distributors - a capacitor. That certainly looks like a capacitor inside the case. Could it be unreliable as you've experienced with your dist issues? Do you have any points distributors in use? If yes, might the capacitors sourced for a distributor be compatible and more reliable?

    EDIT: Were you able to replace the needle bearing set?

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    Default Re: 10si alternator rebuild



    Did you buy the parts individually or a rebuild kit? Are you able to get them locally?

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    Default Re: 10si alternator rebuild



    I just added a bit more....I got distracted in the middle of the write-up and forgot where I left off when I started back.....

    Yes- I did replace the needle bearings - it comes as a cap with needles installed with grease...

    Yes - there is a capacitor that is there to just minimize radio frequency interference. In terms of size, they are too big to fit inside any points distributor that I know of....and I am no longer running points in anything - moved to pertonix in both my set-ups (the 78 sbc going in the willys would have been HEI originally....not sure what I am going to do there yet, but large cap HEI is tough to fit in the willys).

    You can buy the bearings online for $8-10 for the pair, or you can buy a complete rebuild kit which also comes with new brushes and probably new screw insulators and maybe a new diode trio(?) - not sure. I bought the parts locally from D&D auto electric - he rebuilt the old school generator on the 57sbc that I ended up not using for long....highly recommend. I called him yesterday to see if he might have bearings, and he said of course, come on by - $10. After finding the brush issue last night, I took those along with me to the shop today and he got me some of those from his parts pile (lightly used, but better than mine, and FREE)...he also replaced one of the brush housing screws that he didn't like (sloppy rebuild quality he said) and then walked me through a visual check of some stuff, a couple little tricks with putting it back together, and even volunteered to press in the needle bearing for me since driving it in the hard way risks knocking the needles out....all for $10.....I gave him $20 and said THANKS.
    ___________
    James Orofino
    1970 CJ5
    1958 Willys Wagon
    2010 Tacoma TRD

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  6. #6
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    Default Re: 10si alternator rebuild



    yes - on west 44th ave....no website that I know of either
    ___________
    James Orofino
    1970 CJ5
    1958 Willys Wagon
    2010 Tacoma TRD

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    Default Re: 10si alternator rebuild



    That type of service is exactly why I like dealing with small local shops.

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