M30 3.5 with Webers?

[JMinPDX]

Gruppe,

My 74 3.0CSA with the stuck engine from a 10 year slumber sits in my garage waiting for warm weather. I've been working on getting the engine to turn. I've been using MMO in the cylinders with no luck yet. Prepared to pull the head in the spring if need be.

I have the oportunity to pick up a good running 3.5 m30 from an 87 535i for $300. It would come without the AFM, ECU and harness.

Could I bolt up my stock manifolds and a set of webers without too many modifications? I know I'd have to go with an electric fuel pump.
I'll be doing it myself and overall it seems like less work than trying to adapt the Motronic EFI.

Has anyone out there done it this way?

Would I be able to keep the later style distributor without the Motronic EFI? If not is the stock E9 distributor adaptable?

I'm also planning on keeping the stock auto trans (for now).
It's a solid car with a great interior. (52k original miles) But not a show car. I would like to make it a nice driver.

Thanks,

John M

82 e21 Baur
73 Bav
74 3.0CSA
90 Toyota FJ62

 

[x_atlas0]

You would need to use the CS upper timing cover and dizzy, along with a cam conversion nut, as the new motor's cam would not be able to turn the dizzy in its current form. This would also mean changing the valve cover over to the original one, as the upper timing covers have slightly different bolt patterns where they meet the valve cover.

As to the Webers, it depends on what kind. Dual 38s have done well, but the 32/26 Webers run out much earlier, given they run out up top on the stock 3L. Triple 40s will work just great.

Overall, however, it might be worth it to try a different engine instead. The M30B35 is a considerably better engine in every respect. (Higher CR, bigger valves, hotter cam, better head)

 

[JMinPDX]

Funny you should mention an M30B35. I've come accross a low milage M30B35 an hour from my house (From an 88 735i) for $500. Would same mods apply as with the M30B34?
He'll include the Motronic ECU and harness for $100.

John M

 

['69 2800cs]

John-I can't answer any of your questions, I'm new to coupes, but my recently purchased 2800cs has a 3.5 with dual webers. I'm pretty sure they are 32/36's as the linkage is progressive.

I'm in Moorestown NJ. If you ever make it down this way you are welcome to drive my coupe and see how it was done. I have a ton of receipts with the car and the rebuild info may be in there as well.

todd.simpson (at) comcast.net.

Good luck either way.

 

[x_atlas0]

Funny you should mention an M30B35. I've come accross a low milage M30B35 an hour from my house (From an 88 735i) for $500. Would same mods apply as with the M30B34?
He'll include the Motronic ECU and harness for $100.

John M

That is a pretty fair price, and that is the exact source model you want it from. If you kept the carbs, you would need to make the same modifications as you would to the B34, so the upper timing cover, the dizzy, the oil pump, and the CS oil pan. The latter two items would be required for any later M30, due to the CS's front subframe.

If you switch to the Motronic 1.3 (which is significantly better than the 1.0) you would also need to swap in a Motronic external fuel pump, leave the ignition system alone, make a fuel return line, figure out the wiring, (which is fairly straightforeward, actually) and lastly, figure out what kind of intake manifold you want to use. If you want to use the B35 manifold, you have to change the brake booster to a 2002tii booster, as it is the only OEM one I know of that will fit. You can also try to use one of the earlier log-style manifolds, but the wiring (modifying the B35 harness to work with the older manifold) with those is substantially more tricky. I have not tried this approach, however.

The "easiest" larger diaplacement indution system is the dual 38 Webers, or the stock Zeniths, which work suprisingly well with the 3.5, when correctly jetted.

Bear in mind that any engine swap isn't exactly easy. Also, your auto will likely croak under the additional load, as they are apparently very fragile boxes, and often failed with the stock engine. It is the perfect time for a 5 speed swap, if you want to do it.