3.5 Swap Questions

[BarryG]

My 3.5 motor swap is slow but it's coming.Using a 1986 Block from a 535i.I am doing a trial fitup of the altenator.Any advice on using the oraignal 1972 bracket & alt, or the 86 bracket and alt that will also need a wire harness to alt redo.
Thanks Barry

 

[TILLA]

I personally would go with the 86 alternator, it has an electronic internal regulator instead of the mechanical external one next to the battery and has about twice the amperage. As far as re-wiring, since the alternator has the regulator built in you would just need to connect the D+ from the alternator to the D+ wire connection that would go to the external regulator - that branches off to the idiot light on the dash.

 

[jmackro]

Discussing alternator for engine swap

While I can't disagree with what Tilla has written, just to present another side: Why not keep the '72 alternator? While an '86 might have a higher amperage limit, so what? You'll never need those additional amps unless you install power seats, heated cupholders, a 200db stereo, etc. etc. Further, solid state regulators are readily available for early Bosch alternators. They're cheap, foolproof, and bolt-in replacements for the old mechanical regulators.

Keep the '72 alternator, spend $30 bucks on a solid state regulator, and you will achieve reliability without having to fool with the wiring.

My question is: What sort of an induction system are you running with the 3.5 - carbs or FI? Can the original intake manifold & carbs be used with a larger displacement engine?

 

[Bill Riblett]

Another vote for the later alternator and bracket. Not only does the alternator have more output, but the adjusting bracket is easier to use and works better than the original.

 

[BarryG]

The Later setup it is.It just go with the block.The 72 bracket does not line up with the 86 block.
Now the wire harness.There is a 3 plug that went into the old Alt....
Black/Blue/Brown.... Big red ../Battery...Will need some help there.

Also using the 86 bracket I will go with the 86 Power steering pump..should be OK.

Jay.. The induction system ...I am going to use the old log " AIR ACCUMULATOR "..Changing to Motronic/Wire Harness from a 89 635csi.

 

[TILLA]

Look at my previous posting - connect the D+ from the alternator to the D+ wire connection that would go to the external regulator and leave everything else alone.

 

[x_atlas0]

Actually, I'm not sure about the 86 PS pump. That system, if I recall right, was tied into the brake system, which was the "brake bomb" type, rather than the brake booster type that was on the CS originally.

If I recall right, the later PS pump has an extra out which went to the brake system. You will need to plug it.

 

[Dickie]

Barry, best of luck with the swap, I did exactly the same swap last year and has been a year of trouble free, speedy motoring.
Have a look at the pics on this link. By sheer chance my next door neighbour also owns a red M535i.
http://homepage.mac.com/dickiedawson/PhotoAlbum12.html

I can't remember which Alternator bracket I used but I know one of the two definitely worked.
If you have any other questions I can't answer feel free.

Dickie

 

[gazzol]

The Later setup it is.It just go with the block.The 72 bracket does not line up with the 86 block.
Now the wire harness.There is a 3 plug that went into the old Alt....
Black/Blue/Brown.... Big red ../Battery...Will need some help there.

Also using the 86 bracket I will go with the 86 Power steering pump..should be OK.

Jay.. The induction system ...I am going to use the old log " AIR ACCUMULATOR "..Changing to Motronic/Wire Harness from a 89 635csi.

The big red wire is easy, the other one you'll need is the blue one from your plug this is the wire that will turn off your charge lamp. if you wish you can leave the old voltage stabilised in place it won't do any harm, also make sure the blue wire goes into the correct terminal on the alternator as one is mearly a point to connect a noise supressor.