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  1. #1
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    Default VT 5L Alternator into VH 308

    Hi all,

    Apologies if this has already been answered but I couldn't find any details.
    I have a VH SLE with a 85a upgraded alternator from a VN, but I'm not getting the best idle charge.
    I took a look and replaced the brushes just in case that was the problem (they were worn) but no real difference.
    Was going to get it rebuilt but after doing some research found the 85a alternator only push ~14amp at idle rpm? (someone correct me if I'm wrong)

    I was wondering if the VT 5.0L alternator is a bolt on job or if I needed to do any modifications to make it fit?
    Everything in my engine bay bracket wise is stock as a rock.


    Cheers in advance

  2. #2
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    If the alternator is the same as the VN-VS one, you've just got to chop off one of the rear legs on the rear housing and ideally run thicker wire to the B+ terminal and battery negative to engine earth.

    I had the same issue with my stock alternator on my VS Caprice - they're useless at idle, lights, HVAC on and wipers and it stopped charging at the traffic lights and power windows barely moving.

    All fixed with 120A VT alternator and wiring upgrade, solid 14.3V at idle now.

    ANB230 is the aftermarket JAS Oceania part number or Bosch BXH1250A for Bosch, these have the required V belt pulley rather than VT Serpentine - can source through Burson, Cooldrive Distribution and Ashdown Ingram can cross reference these numbers.

    Crappy 80A VS alternator:



    ANB230/BXH1250A next to 80A VS alternator:



    120A ANB230/BXH1250A fitted - you can see where I butchered off the rear mounting leg with an angle grinder:

    Last edited by Daymoe; 19-02-2019 at 11:35 PM.

  3. #3
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    Thanks Daymoe!

    Yea mine looks exactly the same as the stocker unit you had.
    Thanks for all the part numbers and photos too they will come in handy -- looks like all I need to do is the V belt pulley change + grind off that leg at the back once I get the alternator itself.
    I recently did the wiring upgrade too thinking it might help with the charge - previous owner did the 85A upgrade unit but did all sorts of splicing/joining/running different gauge wires. Now its running straight 4 gauge to the batt terminal + upgraded grounds.

    Gotta be honest I cant believe how low the output is at idle for an 85A rated unit. I mean the photos of yours look brand new so that leads me to believe maybe mine isnt so worn it's just how they are?
    Any hopes of me running extra accessories / thermos would cause major issues - I'm barely creeping 12.7-12.9v at the moment idling in drive with the headlights/stereo/usual accessories on at night.. I watch the volt gauge bounce around when I put my indicators on with all my other stuff on hahaha

  4. #4
    Sure why not? 76lxhatch's Avatar
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    I'd think it would be more than 14A, but it may well be lacking depending on engine idle speed and pulley ratio. If you buy a decent unit it should have a published graph or table of output so you can tell what the maximum current supply will be with your specific idle speed (don't forget the alternator is spinning probably at least twice engine speed). If you can't get the rpm high enough start looking at your pulleys.

    I ended up with a VZ LS1 140A unit, it supplies at least 90A (if memory serves) at ~2000rpm (my engine idles at 925rpm, pulley ratio ~2.1:1). Not a direct bolt-on as it has mounts 90 degrees apart rather than 180 but not too much mucking around.

    Only thing is it seems to load up immediately on engine start and can make the V belt slip a little, working on a fix for that.

    The pulley is pretty well interchangeable on all these units so you can swap the serpentine to V belt easy enough. You may need to adjust the spacing to get the right belt alignment but that's usually necessary with any swap.

  5. #5
    Not the Kingswood! hq308's Avatar
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    Another option is to use an aftermarket alternator for a Chev. It just needs a 5mm thick spacer to mount in the standard Holden bracket and a 3mm spacer behind the pulley to get the correct belt alignment.

    Easy to make or you can buy them pre-made https://www.aeroflowperformance.com/...-alt-to-holden

  6. #6
    Sure why not? 76lxhatch's Avatar
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    Quote Originally Posted by hq308 View Post
    Another option is to use an aftermarket alternator for a Chev.
    If you go that way make sure you get the detailed info on what the output is based on rpm, some are fine but many are worse than the VN alternator.

  7. #7
    254RWHP boat anchor EVL253's Avatar
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    the bigger 120amp alternator i tried on early heads with the stock drivers side bracket the back hit the spark plug so wasnt usable
    11 second E85 bottle fed boat anchor

  8. #8
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    Thanks for the replies all; Iíll have to have a look into it.

    EVL253 you make a good point Iím a bit worried now about the VT unit fitting as my current alternator is fairly close to the plug wire Iím not sure the new one will fit there

  9. #9
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    Quote Originally Posted by roccoloops View Post
    Thanks Daymoe!

    Yea mine looks exactly the same as the stocker unit you had.
    Thanks for all the part numbers and photos too they will come in handy -- looks like all I need to do is the V belt pulley change + grind off that leg at the back once I get the alternator itself.
    I recently did the wiring upgrade too thinking it might help with the charge - previous owner did the 85A upgrade unit but did all sorts of splicing/joining/running different gauge wires. Now its running straight 4 gauge to the batt terminal + upgraded grounds.

    Gotta be honest I cant believe how low the output is at idle for an 85A rated unit. I mean the photos of yours look brand new so that leads me to believe maybe mine isnt so worn it's just how they are?
    Any hopes of me running extra accessories / thermos would cause major issues - I'm barely creeping 12.7-12.9v at the moment idling in drive with the headlights/stereo/usual accessories on at night.. I watch the volt gauge bounce around when I put my indicators on with all my other stuff on hahaha
    Yeah I put a new 85A alternator on it because I thought the factory one was halal, the new one did the same thing the bastard, they just don't charge for shit at idle unfortunately which is rather lame, it was causing strange electrical issues around idle on my car with its aftermarket ECU, idle problems, stalling etc when she'd drop to around 11V at idle with everything on and the battery was getting tired.

    New battery, new alternator, idle with the accessories on it was doing the same as yours, 12.5V which means no charging and the indicators being on would make the dash lights go dim, bright, dim, bright with them flashing, or they'd dim with brake lights on.

    With the alternator itself, if you order BXH1250A/ANB230 - it comes with the right V pulley:

    https://www.speedspares.net/ANB230_p/anb230.htm


    https://www.ebay.com.au/i/323656030780?chn=ps

    EVL253 might be on the money with fitment issues if there is an issue with the early heads and stock bracket as the VT alternator has internal fan so the body of it is a fair bit wider - is there a bracket you can change to? Or maybe good excuse for VN head upgrade
    Last edited by Daymoe; 20-02-2019 at 11:15 PM.

  10. #10
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    Quote Originally Posted by 76lxhatch View Post
    I'd think it would be more than 14A, but it may well be lacking depending on engine idle speed and pulley ratio. If you buy a decent unit it should have a published graph or table of output so you can tell what the maximum current supply will be with your specific idle speed (don't forget the alternator is spinning probably at least twice engine speed). If you can't get the rpm high enough start looking at your pulleys.

    I ended up with a VZ LS1 140A unit, it supplies at least 90A (if memory serves) at ~2000rpm (my engine idles at 925rpm, pulley ratio ~2.1:1). Not a direct bolt-on as it has mounts 90 degrees apart rather than 180 but not too much mucking around.

    Only thing is it seems to load up immediately on engine start and can make the V belt slip a little, working on a fix for that.

    The pulley is pretty well interchangeable on all these units so you can swap the serpentine to V belt easy enough. You may need to adjust the spacing to get the right belt alignment but that's usually necessary with any swap.
    Thats a mad setup, I would have been keen on that, I think the issue is the V belt setup struggles to handle the load a 120A+ alternator will put on it:

    7.BELT and Pulley Size vs. Amp Loading (at 12vdc)

    One of the most common questions asked. What is the smallest or largest belt / pulley combination may I install on my engine, water pump, alternator, .... The combinations of this question with different variables is endless. On your existing engine system, whatever the manufacturer designed it to have is what you have to live with without modification (Westerbeke is the only exception we have found to this rule, but not really because they were designed for higher loads even though the standard installation is a single 3/8" v-belt.).

    To increase your basic installed belts and pulleys beyond what they were designed for - Did you read 7?

    Bottom line is as follows:
    • single 3/8" vbelt supports up to apx. 70 amps
    • single 1/2" vbelt supports up to apx. 94 amps
    • double 3/8" vbelts supports up to apx. 140 amps
    • double 1/2" vbelts supports up to apx. 300 amps
    • single 8 groove serpentine belt supports up to apx. 300 amps

    Exception to carefully note: If your use a single 3/8" belt exceeding 70 amps up to a 94 amp load, be aware it will work, but possible ramifications are increased side loading of the water pump, alternator, and v-belt. This will probably decrease water pump and belt lifespans significantly. Extra spares are a must - Do not forget a spare water pump, not just the impeller. The corresponding limit for a single 1/2" v-belt is 120 amps.
    ZRD FAQ - Belts and Cables

    The only other option I reckon is maybe see if you can get more belt wrap around the alternator pulley somehow.

  11. #11
    Sure why not? 76lxhatch's Avatar
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    I'm working on some pulleys to allow a multi-rib/serpentine belt setup. The factory VT config used a couple of short/narrow multi-rib belts (in much the same fashion as a normal V belt).

    It only slips when starting, never after that. I think this has more to do with the fact that the sensing system causes immediate load, later vehicles changed to ECU control and clutch pulleys, I wonder if this is one of the reasons. It won't be delivering all 140A all the time, that would be another problem. Those numbers also appear a little conservative when you look at factory configurations.

  12. #12
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by Daymoe View Post
    ..................... maybe good excuse for VN head upgrade
    screwed alternator?
    yeah lets change the heads

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  13. #13
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    Quote Originally Posted by Daymoe View Post
    Or maybe good excuse for VN head upgrade
    hahaha I like this thinking....
    Hindsight is a bitch - I got the heads that were on it L34 specced, shaved, ported and polished on such a mild engine.
    I wish I did the VN heads because now I'm even looking into Holley EFI which I could have just grabbed a VN top end and got the chip/tune to suit the configuration.
    ahwell eventually Ill get it right

    After all the suggestions I got some measurements of the VT alternator and compared them to the stock one; as EVL253 said I'm almost positive it wont clear - VT alternator is 14mm bigger length wise so there's no hope itll fit in front of the plug / lead.

    See pics for reference

    VN-VS 85a style - BXH1231
    BXH1231AA.JPG

    VT style 120a alternator - BXH1250
    BXH1250A.JPG
    Attached Images Attached Images
    Last edited by roccoloops; 21-02-2019 at 01:31 PM.

  14. #14
    casual poster NOHOPE's Avatar
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    Quote Originally Posted by hq308 View Post
    Another option is to use an aftermarket alternator for a Chev. It just needs a 5mm thick spacer to mount in the standard Holden bracket and a 3mm spacer behind the pulley to get the correct belt alignment.

    Easy to make or you can buy them pre-made https://www.aeroflowperformance.com/...-alt-to-holden
    I went with this option, 120amp unit from the states. Tuffstuff is the brand. Old school shape with external fan, if anything I ended up with more clearance to the plug. This is with early heads.

  15. #15
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    I am running the Bosch BXH1253A 120A in my HX - early heads.

    Using a gilmer belt, obviously no slippage. Only a small mod required to the H Series alternator bracket (filing off part of the mount).

    Not sure if that helps the OP.

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