1986 325e M30 Swap Wiring Options

[Stuffing]

UPDATE: Latest post here

Hey all, first post here.
I've got a 1986 325e that I'm in the process of engine swapping with the M30B35.
I haven't been able to get any comprehensive info on how exactly I should go about getting the engine wired up. I was aware of the additional wiring difficulties I would face by getting a 1986, and now I'm trying to figure out how to get past them.

Basically: What is the easiest way to do this? I've heard of people just wiring the M30 engine harness up to their M20 ECU, but I don't think this will work in my case. Should I try and find an e34/e32 M30B35 ECU AND the wiring harness from the same car? I'm having a hard time finding any in my area so I'm wondering if there's an easier way to do this. My friend and I have 3 M30s (yeah, I know...) but only 2 ECUs for them so my donor car won't be able to provide it.

One other thing I haven't seen any clear info on: I've heard people say that my 1986 325e manual driveshaft should fit the M30 and tranny fine, but which engine position would this require? I'd rather not modify my current/buy a new driveshaft.

Really excited to get this thing rolling so I can show it off. ;) Thanks guys.

[Mr. Burns]

hey

yes your driveshaft WILL fit as it is as it has the large tranny output flange. so no need to buy a new driveshaft or modify it.

as for engine fitment, you will need to hammer in about 1" at the firewall or a bit more (I went a little overboard and did about 3"..don't do that) Clearance is for the head to fit.

If I were you, and to avoid futher complications- I would simply swap in the M30 wire harness from the engine you're using.
NO you cannot use your 325e ECU with the M30. you'll need the "179" Ecu that came from M30b35's

I completed my swap with a M20b25 wire harness, but I ran into a couple of issues that have since cleared. Also, the M30b35 harness will offer a cleaner more "finished" look.

There are 179's ECU's available aplenty. just check ebay, forums, here...they're around.

[CorvallisBMW]

Mr Burns, is correct on all counts. If you need an ECU, I have one for sale right now with the sssquid tuning chip (best tune out there for otherwise stock m30b35 motors, runs perfect and pulls hard). Shoot me a PM if you're interested.

[Stuffing]

Awesome, thank you both for the info. Seems like avoiding any hassle with the driveshaft may have been worth the extra wiring effort.
An ECU shouldn't be too hard for me to find, and we don't need all of our M30 cars running right now so I may just pull the wiring harness and/or ECU from one of our 535i's for now.
I'll send you a PM if I need an ECU from you Corvallis, but I'll probably have one available. What I really need to do is explore the junkyards around here for some trashed e28/e34 535i's and get parts from those but I've had a hard time finding any so far.

[lukeADE335i]

Depends on which mounts you have too as to whether you need to hammer the firewall or not.

I have the M30B35 e30.de mounts with the engine in Position 3 and only hammered the firewall back by about 1/8th of an inch. I could have got away with almost no hammering at all. On RHD cars there's a brake linkage to consider & so we can't bash the firewall like on most of the LHD swaps I see on here (LHD would have been easy vs. mine!)

The guides that talk about hammering the firewall were often dealing with the coolant neck at the back of the head of the M30B34 (which would definitely require hammering by around 1 inch) but the M30B35 has this blanked off & has more room at the back of the head.

I think the Garagistic mounts place the engine back even further back than what traditionally has been called position 3.

[Stuffing]

Opening this back up for a progress report...

I've got the engine in now - the Garagistic mounts worked great but using the stock bolts we ended up needing to fab some spacers since the holes were so big. Here's the bay:


When trying to fit the driveshaft we ran into a problem, however. The guibo from my 1991 535i donor looks too big for my driveshaft:


Another view:


It looks like my driveshaft flange is too small despite being from a 1986 325e. The guibo from my e30 is totally trashed so I'll need a new one if that's the size that should be used, but the concern I have is that it doesn't look like it would fit on the new transmission.
Another thing I noticed is that the 325e guibo got larger after 5/1986, and based on my VIN my car is from 4/1986... Does this mean the driveshaft flange also got bigger? Am I going to need a new driveshaft?

[lukeADE335i]

Nice work - looks as though your engine is sitting well back, which it good!

Unfortunately you missed out on the large flange driveshaft it seems, which means you either need get a later eta driveshaft, or you could mod your existing one by having the flange cut off and a large flange added, or swap the gearbox output flange over to a small one to suit your driveshaft (the M20 G260 output flange can be fitted to the e34 gearbox).

On the upside, looks as though your driveshaft is the right length, so a stock eta driveshaft with the large flange should fit.

[Stuffing]

... swap the gearbox output flange over to a small one to suit your driveshaft (the M20 G260 output flange can be fitted to the e34 gearbox)...

That sounds like the best idea, I'll go with that first. Thanks!
I'll keep updating this thread as things progress.

[Stuffing]

Alright, next update.

I was able to get the output flanges off both my transmissions, took a fat impact gun to get em off though (In case someone reading this is doing the same thing - I used a Black and Decker 1/2 Bulldawg with this socket. The socket didn't hold up too well from the punishment but the walls were thin enough that I didn't need to modify it.)



While I had all that clearance, I decided to see if I could get the e30 plate-style shift linkage to work.
It looks to me like the plate and shift arm are exactly the right length and don't need shortening, but there's a problem.



Those two holes on either side of the shifter arm spot are too small and are unthreaded, so the old plate mounts won't bolt in without modification to the transmission.
Any ideas on getting the plate-style shifter to work, or should I go cut an e34 shifter? I'd rather not take my friend's and cut it up, but he's offered it to me anyway.

[lukeADE335i]

The late 325i aluminium shifter arm should do the trick seeing as the plate is the right length.

[Stuffing]

Update:
Shifter assembly installed - it turned out to be fairly simple just threading the unused plate-shifter holes in the G260 so that was the route I took. In retrospect, it would probably be better to just find a newer non-plate e30 shifter, but whatever. It's in now, and it shifts pretty well!

Engine position corrected - The engine was a bit crooked when we first got it in and it's actually still just barely nudging the brake booster. Seems OK now but we'll see when it starts driving around.

It runs! - I wired everything up with the M30 harness that came with the engine. Made almost no modifications and the car started on it's first try! I'm getting CEL but I know at least one definite cause for it (o2 sensor) so I'm not too worried.
My tachometer does not appear to be working, is there some extra wiring I need for the 1986 325e shell?
EDIT: Never mind, I figured out where the wiring for this goes (in addition to the fuel consumption reader).

Next up is getting the cooling system installed, and since this is a pre-facelift shell it will be a little more difficult. I'll get you guys some pics when we actually have daylight here.

[Coupelx]

I was just about to post that not all of the 86 325e's were large guibo, mine is a small guibo. But it seems you have already figured that out!

[Stuffing]

Alright - here's some more pictures of the engine bay as it is now.



I have all of the cooling hoses installed now. Problem is, this being a pre-facelift shell, I can't use the old coolant reservoir location for obvious reasons. Extra wiring floating around here will get moved into the glovebox once I get the firewall hole enlarged a bit:




I'll need to put one somewhere in here probably, but I don't see any bracketry in there for a newer 325i or e28 535i reservoir. Might not be hard to just move mine over. Anyone know of any builds that have done this? The hoses and t-piece would be pretty easy to get, though.



Here's my clearance to the front. Radiator not in but it does fit with a bit of room:



And a snap of where I'd like my 325e reservoir to go:



I also tried using an e34 reservoir right on the firewall, but I can't get it to fit under my hood, and I'd also like to put a strut there at some point which could get in the way.

[Mr. Burns]

I have a preface lift e30 amd managed to get the e34 coolant reservoir to fit along the firewall.
It just makes clearance to the hood, yours should fit too.
I secured mine with zipties.

Depending on the rad you went with you may need cut/Dremel off two lower oem rad mount tabs.

Looking great so far congrats!

[CorvallisBMW]

See first page of the thread in my sig, there's a photos of my bay in there. Any late-model 325i reservoir fits perfectly on the stock brackets.