M40 to M20 conversion

[taldo50]

now then!!

i want more power in my touring and been pondering an engine swap, and decided to start gathering parts/info to do the deed in the spring/summer, just wondering what to put in the old girl! and how easy it is because im afraid im a bit of an amateur with the spanners! im not bad but also not brilliant. but i reckon i can do it. maybe with a little advice!

shes currently got a lovely little M40 1.8 and i want to put a m20 2.5 in.

Is it difficult should it just be plug and play with regard to wiring etc?? obivously i should do a little work to the engine before it goes in, service etc but anything else you guys can suggest?

just after a little advice/wisdom really

also would it be easier to drop a M42 in?

this is all just to wet my beak in the engine swap department as id love to have a crack at an m30 conversion one day, but im a little scared of that, and also short of the nessecary spare cash for an m30 at the mo!!!

so a little m20 or m42 swap will suffice for now !!!

cheers for any help u may be able to give guys!!!

[suzie650]

Both swaps you are considering are fairly straight forward, as the E30 was designed to recieve these engines.
Provided you get all the engine/loom/gearbox bits, you might have the odd bracket missing and a couple pins to change on the engine to car loom connector (C101), but that's all.

To the M42 vs M20, if you already go for swapping an engine, why would you put the 4 pot in? Especially in a touring, the I6 doesn't make the handling awful, goes better and sounds much better!

And as for the work to do, the tricky question when putting an engine in is where to stop... I'd love to rebuild fully the engine I'm putting in mine, but it would cost sooo much to do properly... More than the engine cost me in the first place! To be half reasonable, I think there are two options: Buy an engine as cheap as possible and rebuild it fully yourself (time and money consuming), or buy a engine you know is good and don't bother about doing anything to it.

[Brianmoooore]

and a couple pins to change on the engine to car loom connector (C101), but that's all.

Not if your fitting a M42 or M20 that came from an E30.
Read my 'sticky' engine swap wiring warning, though!

[taldo50]

cheers guys seems reasonably straight forward by the sounds of things the tricky bit is going to be finding a decent m20!!! a donor car sounds like a good idea! then flog spares from it to help ease the financial burden!

suzie 650, notice you got a little bit at the bottom of your post that says m20 conv kit for sale again? how much?

also another query i should probably chenge the diff 2? how hard is this to do? a least i dont have to change to rear discs as i already have a touring!

[Ayrshore]

shame you're so far away, if you were more local I could have sold you a good M20 or two...

[taldo50]

i believe thats called sods law!

[bruvs1]

i have a rotten 325i 4 door with a sweet m20 that i'm going to put into my `new` LHD (dont ask ) m40 tourer (has a dead cam etc,etc). I have noted your sticky Brian with thanks. Will the Left hand drive issue catch me out on anything?
Thanks
John

[suzie650]

Not wiring wise anyway - lhd and rhd are the same as far as I'm aware

[bruvs1]

i've removed all the 325i donor running gear now and engine loom. I have also checked the pin 20 on both cars, they both have the red/yellow wire . Am i correct in saying i can leave the dash wiring in place and just swap the clocks over to suit the six pot?
Thanks

[Brianmoooore]

i've removed all the 325i donor running gear now and engine loom. I have also checked the pin 20 on both cars, they both have the red/yellow wire . Am i correct in saying i can leave the dash wiring in place and just swap the clocks over to suit the six pot?
Thanks

Only thing you need to change on the clocks, is the little white coding plug on the lower front face, just below the ignition light. No need to remove the clocks, just the trim pieces below and around them, then pull out the four pot plug and replace it with the six pot one.
Pin 20 should be OK, if both cars have the red/yellow wire, but it's pin 20 on the car side of the C101 that needs to be checked for a brown wire, and removed if present.

[bruvs1]

Thanks brian, even better i'll just swap the plug as you say. If the car side is the fuse box side then we should be ok.
One thing i've noticed is that the rear valance will need a cut and a return edge. My next job is to open up the sump and see if the six pot is as good as it sounds. Will get some photos next weekend when i'm getting everything cleaned up.

[jmc330i]

One thing i've noticed is that the rear valance will need a cut and a return edge.

Is that for the exhaust?

[bruvs1]

yes i'm thinking for for the extra pipe, as theres a nearly new system on the donor.

[jmc330i]

Its a shame its a nearly new system, I modded my 325i backbox so it had a single 3" pipe that fitted the 318i valance. Looked like a 318i with a bigger tailpipe, but sounded great....

M20 sound

M20 drive-by

[bruvs1]

i agree the 2 JMC's think alike!

[bruvs1]

i've just noticed a few more m40 > m20 threads but i'll stick with this one:
here our new m40 tourer shell:


heres the engine its a 6k, alot cleaner than when we removed it


had sump off + main/thrust cap off and its in good nick, rocker assembly clean too. Replaced the cambelt too and checked the clutch its ok. Someones snapped 3 manifold studs off in the head but they'll come out.
Now i'm gonna order some new engine mounts up and get a shift seal for the back of the box. Read the oil grade sticky, but bearing in mind this things gone round the clock do i want type do i want mineral or semi-synthetic?

some bad news though....the 3.73 diff feels sick?? when i rotate a driveshaft flange (its not a limo) the other flange rotates the opposite way and in doing so feels very rough. When i turn both flanges forward it feels better

i'll get some more info on soon i hope...

[suzie650]

That's probably an open diff, then.