The comprehensive DOHC engine swap thread.

[1990m3]

e21 is heavier according an article I just read last night in Classic Motorsports. Don't know weights, they just said the E30 was lighter and more powerful than it's predecessor in some little caption at the bottom of the page

stick with the e30, its such an easy swap

[02stu]

I wouldn't do the e21 route, you have to put alot of money into those cars to make them perform and when your done it won't be worth anything. Plus the chassis and drivetrain will not hold up. The one person I have talked to that did that swap had stress cracks althoughout his front shock towers. He eventually had to put in a full cage just reinforce the front. Also the differential and driveaxles are weak. E21s use a small case diff with drive axles only slightly larger then 2002 units. Also to do the swap you will need to get a hold of a e21 323i front subframe, this won't be easy or cheap since they are rare. Finally wiring it up is very difficult since you will be starting from scratch and running an entire wiring harness. So if I were you I would start with a e30 which not only will be rust free, lighter, wider, stiffer, etc. Untill a year ago I was trying to put an M50 into my 2002 untill after and hundreds and hundreds of dollars down the drain I bought an e30.

[joshh]

I found something intresting. Maybe it's simple for a few of you but my 92 525i Motronic 403 green label has an orange sticker on the bottom of it. It's round and says "BMW SERVICE ACTION" around the outside perimeter and "DME CONTROL MODULE REPROGRAM" on the inside area.
What the hell does that mean?
Any help would be much appreciated.
I can call the dealer tomorrow and find out.....

[Brew]

There was a Service Bulletin put out by BMW back in the day to reprogram those DMEs if a customer complained of certain running problems.

[bigmick13]

alright so i read through this whole thread. but im still kinda unsure about one part. if i use my stock 5-speed from my 86 325es will it bolt right up to an m50 bellhousing?

[joshh]

Yes all but the bottom 4 holes. It will bolt up to the block.

[m3needer]

im having trouble with my transmission mount i have the ZF tranny mated to the m50 / when i tried to bolt on the 320 tranny mount it wouldnt fit any suggestions can you post a pic of yours thanxs in advance

[BeirBrennerE30]

i have 2 conflicting wireing diagrams... that ill post right here since there seems to be a lack of info on this on this thred... everyone can debate which of the 2 diagrams is the correct one or maybe a hologation of the 2... so here it is...

e30 plug pin#.... to e36pin#(diagram A).... to e36pin#(diagram B)
1............................25................... .....................................25
2............................16................... .....................................16
3............................NA................... .....................................NA
4............................12................... .....................................12
5............................23................... .....................................23
6............................22................... .....................................22
7............................21................... .....................................21
8............................24................... .....................................24
9............................20................... .....................................20
10..........................10.................... ....................................10
11..........................19.................... ....................................NA
12..........................8..................... .....................................8
13..........................13.................... ....................................13
14..........................14.................... ....................................14
15..........................15.................... ....................................15
16..........................NA.................... ...................................19
17..........................NA.................... ....................................18
18..........................18.................... ....................................NA
19..........................NA.................... ....................................NA
20..........................NA.................... ....................................3

[325Projectz]

im having trouble with my transmission mount i have the ZF tranny mated to the m50 / when i tried to bolt on the 320 tranny mount it wouldnt fit any suggestions can you post a pic of yours thanxs in advance

Care to explain more? But if its what I'm thinking...
Drill the holes out on the mount, and shave the threads on the top (tranny side) mount, just so they can slide into place.

[BeirBrennerE30]

also... i have a few other topics to discuss....

1. How much clearance to get get between intake mani and 325ix booster??? is it worth it to modify the 320i booster(ie does it provide much more clearance?) and what is the largest MC you can fit with each booster and from what car??

2. Will 535 (some say 533)motormounts work with no spacers??? can you get the engine to sit lower than it does with e28m5 mounts???

3. Anyone used an e36 radiator? what does it take to get it to fit(ie can you use BMW parts to fit it and do you still need an overflow tank??)

[325Projectz]

also... i have a few other topics to discuss....

1. How much clearance to get get between intake mani and 325ix booster??? is it worth it to modify the 320i booster(ie does it provide much more clearance?) and what is the largest MC you can fit with each booster and from what car??
Brake booster info, post #22

2. Will 535 (some say 533)motormounts work with no spacers??? can you get the engine to sit lower than it does with e28m5 mounts???
I'm pretty sure that the e28 535 and e28 m5 mounts are the same, or atleast they are going to sit at the same height. Most that used the 533 mounts need spacers.

3. Anyone used an e36 radiator? what does it take to get it to fit(ie can you use BMW parts to fit it and do you still need an overflow tank??)
Get a e36 radiator, e30 late model overflow tank, and the e30 late model bracket

All of this has been gone over before, FYI.

[BeirBrennerE30]

All of this has been gone over before, FYI.

1) post 22 is about trannys... ummm??? i need a new booster so i want max clearance with minimum effort and i dont feel like modding another 320i booster... are all 25mm MC interchangable???

2) yes i know but can you get engine lower with 533 mounts... i have m5 mounts but i want the weight as low as possable so i wanted to know if it would be better to switch

3) i didnt know that the stock e30 bracket would work and i dont think rad fitment was covered... fluidyne here i come

[325Projectz]

Brake booster info, post #22

That is a link...

[FredK]

2) yes i know but can you get engine lower with 533 mounts... i have m5 mounts but i want the weight as low as possable so i wanted to know if it would be better to switch

I believe people running 533 mounts need spacers to clear the rack.

[DanGillan]

i didnt have to.

90' with an ABS steering rack. no spacers. 535i green mounts.