Alternator Bracket - Wrong parts?

[jhh925]

I'm in the process of re-building my 87 535. The motor will end up being a combo of B34 and B35 parts, but relevant to this question, the bock, alternator and alternator supporting bracket are all off of the original B34 motor that was in the car.

Yesterday when I went to reinstall the alternator supporting bracket, I ran into some strange stuff. I'm now pretty nearly certain that at some point in the car's past, the wrong alternator adjusting bar (BWM part #12311714922, item #12 in this RealOEM diagram) was installed. When I took the current adjusting bar off of the supporting bracket, the rear flange of the adjusting bar with the welded-on bolt in the pics had been bent back to allow it to fit onto the supporting bracket. When I bent it back, the adjusting bar opening is about 2-3mm narrower than the mounting flange that it's supposed to fit onto.

Further, note in the pic below that the supporting bracket is threaded where it butts up next to the adjusting bar. The RealOEM diagram shows that the securing nut is separate from the adjusting bar. And this design (two adjacent parts that are both threaded) would prevent them from being tightened up together when you install the through-bolt. And indeed, the bolt that was in there fit pretty badly.

So, is this the wrong adjusting bar? Or maybe (worse) is the supporting bracket the wrong one? (Note that the numbers on the supporting bracket don't match any BMW part numbers that I can find, but I'm probably not decoding the number pattern on the part correctly.)

Conceivably I could make this adjusting bracket work (grind off the nut, bend the rear mounting flange, use a new securing lock nut), but that doesn't seem like the way to go at this point.

Adjusting bar doesn't fit onto supporting bracket:



Both parts have adjacent threaded holes ... can't be right:



Part number on supporting bracket is 1.1 1 1 274 579.9?:

[demetk]

To make that fit and look neater, I'd grind down the supporting bracket a bit and lose the threads since they're not needed.

I think there are single adjusting bars and that may have been what was originally installed on the bracket. The double bar is much stronger and keeps the alternator in better alignment.

[jhh925]

Interesting. What's the difference between a "double" and "single" bar? To the extent I can rely on the visuals in RealOEM, the diagram shows a part that pretty much looks exactly like what I have in the pics.

Also, assuming I do grind the support bracket down, I just want to confirm I'd grind down the back side of the through-hole (facing towards the rear of the car). I would think the front side essentially is the register to make sure that the mounted alternator pulley lines up correctly with the other pulleys ... right?

[SmokeyJohn102]

Heres what I did for my 140 amp alternator swap on my b34...I used the stock b34 bracket on the block, I used a b35 adjusting bar. To compensate for space on the backside of the alternator I went to the local hardware store and purchased a dowel spacer looking thing I cant remember the specific size but id like to say it was 3/4 or 1 inch. Ill try to snap pics of it tonight for ya although its tight in there. I also had to use a smaller belt. Ill get you specs.

[jhh925]

Thanks all. Good info. Sorry for not posting up the results earlier. Last Friday I went down to the shop where Yar works (German Auto Sport). I was leaning towards grinding the block bracket down, but I wanted to be sure, and after comparing my parts to the B35 stuff he had, that definitely made the most sense ...

[demetk]

That looks pretty good.

[joeuser999]

Doing some research on this myself since the early single/flat bracket is weak and belt tension is pulling my alternator out of alignment. The original bracket is also too short for the 12x1050 belt the parts shop sold me.. I think my early e28/535i technically calls for a 12x1040 alternator belt

I want to switch to the double bar and find them discontinued in 2024..

For posterity...

The early m30b34's used the single/flat bracket, pn: 12311274747

The later m30b35's used a different alternator base bracket along with the double sided adjusting bracket, pn: 12311714922

The e34 & e30 5 series both used a similar-but-different double sided bracket that is available in 2024, pn:12311714450
No certainty of an easy retrofit of the e34/e30 bracket to the e28/m30b34 alternator bracket