Updating old body altenator to later style.
11-10-2014, 04:45 PM
#1
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Thread Starter
Updating old body altenator to later style.
Have a 1984 928s. It's original alternator is long gone and the Bosch 90amp replacements that were installed are a bit weak. Worst of all they don't have fitment for the cooling shroud. I've got a more powerful alternator from the later cars( shared with 86 And later 944's). What is involved with putting the newer alternator in my car? I did some internet and parts fisch investigation and it looks like with the introduction of the S4 block the brackets for the alternator were changed too. A conversation with Tom at 928 International brought me the information that its been many years since anyone had done this. Apparently the bracket for the S4 alternator can be added to the 16V block. However the block must be redrilled and tapped. Not something I'm thrilled about.
Last edited by sstrickstein; 11-10-2014 at 05:50 PM.
11-10-2014, 06:34 PM
#2
Electron Wrangler
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The new alternator (S4+) with shroud is not really a great performer in high heat either - if you will go to that much trouble I think you will end up being disappointed with the results (likely very similar).
The stock design is just not really good for ultra high heat (like AZ summertime). You don't need more max amps you just need more amps at hot idle.
Alan
The stock design is just not really good for ultra high heat (like AZ summertime). You don't need more max amps you just need more amps at hot idle.
Alan
11-10-2014, 08:07 PM
#3
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Thread Starter
Correct idle amps is my problem. I have a clutch fan delete kit from 928 motorsports. So at idle, in the evening, with the lights on and the a/c my alternator output is way low. In the am with the a/c and the lights off, no issues.
11-11-2014, 09:47 AM
#4
RL Community Team
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Carl at 928MS installed a 200 Amp alternator into my '79 while doing the other work. I believe he had to fabricate and weld a bracket but he might be able to provide some additional info if you get in touch with him. I wanted to upgrade the alternator to support a 1,000 Watt stereo, HID headlights, and some other items.
11-11-2014, 09:59 AM
#5
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I watched Collin install a GM alternator from a local parts store on an 84 at Marble Falls. Don't know all the details, but I think there were a few washers used as shims, and some trial and error to find the right belt. I had never heard of that trick before.
11-11-2014, 10:20 AM
#6
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Don't forget, you are dealing with 30 year old wiring too.
My 81 started to have intermittent cranking issues, upon investigation found some of the pins in the multi connector by the jump post corroded.
While taking that apart to remove / clean / replace those pins, we started to peel back the wire loom running down across the front of the motor. We found the main power wire running to the starter was hanging on by only a couple strands of wire (the rest were green and gone...).
Mike (Z) also took apart every connector on the other end of that loom (starter, alternator, oil pressure sender etc...) and cleaned them all up.
Once this wire was replaced and the connectors cleaned up, I want from the volt gauge bouncing under 12 at idle to above 12, no matter how much stuff was turned on, and my car has electric fans and a high output electric water pump for the intercooler.
The first time I started the 81 after this repair, I thought the valves were bent it cranked over so fast compared to before.
My 81 started to have intermittent cranking issues, upon investigation found some of the pins in the multi connector by the jump post corroded.
While taking that apart to remove / clean / replace those pins, we started to peel back the wire loom running down across the front of the motor. We found the main power wire running to the starter was hanging on by only a couple strands of wire (the rest were green and gone...).
Mike (Z) also took apart every connector on the other end of that loom (starter, alternator, oil pressure sender etc...) and cleaned them all up.
Once this wire was replaced and the connectors cleaned up, I want from the volt gauge bouncing under 12 at idle to above 12, no matter how much stuff was turned on, and my car has electric fans and a high output electric water pump for the intercooler.
The first time I started the 81 after this repair, I thought the valves were bent it cranked over so fast compared to before.
11-11-2014, 10:38 AM
#7
Developer
Many alternator charging problems can be the engine wiring harness. If the exciter wire to the alternator does not provide the right voltage, the alternator cannot make up the right output. Hacker's experience with the 14-pin connector and the corrosion in the front loom is typical.
We make new engine wiring harnesses for that problem.
As to the alternator - they were the best they had ast the time, but too small then and way too small now given high-output stereos, more common use of electric fans, and such. We make 200 amp alternators for most 928's.
We make new engine wiring harnesses for that problem.
As to the alternator - they were the best they had ast the time, but too small then and way too small now given high-output stereos, more common use of electric fans, and such. We make 200 amp alternators for most 928's.
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11-11-2014, 11:14 AM
#8
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Alternator performance challenges aside, can the later model power ateering/alternator c bracket be retrofitted to the early car, and if so, does the later model alternator then just bolt up? I thought this was true but can any body confirm.?
11-13-2014, 09:22 PM
#9
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A fiddly job that required changing the power steering pump and bracket because the belt order on the crank pulley is different.
Of course the alternator belt is also different on the '81, [A section vs flat ribbed].
The crank pulley also had to be changed to accommodate the flat belt.
The power steering pump bracket needs a bolt into the block that requires drilling and tapping. Doing this in the car meant using a right angle drill attachment. very cramped and takes time and patience to get it right.
It has done many miles now and you wouldn't know anything was different looking at it.
HOWEVER, as has been said, the idle output is still too low for our summer with aircon, electric fan and lights on. Only needs just a few more revs though, say 900 rpm and it's fine and this is with new wiring loom as well but a more modern unit would be my next choice.
