Author Topic: Fitting an m42 in an m20 car. (Read 4302 times)

suhinaffy · « **on:** August 03, 2012, 05:43:23 PM »

Hi, i'm a member of a couple of uk based forums but there's not a lot of info on them about what i want to do. I have a good condition minimal rust e30 325 touring, the m20b25 was running great but the fuel costs weren't great. I picked up a cheap e30 318is for �200 with 10 months mot, it's pretty rotten so i'm planning on taking the engine out and putting it in the touring. The question is, what do i need to take from the 318is? Apart from the engine, box, loom, exhaust, ecu, fuel pump, prop, diff etc? Already removed the m20 from the touring but have yet to start stripping the 318is. Will get some photo's of progress so far.

suhinaffy · « **Reply #1 on:** August 03, 2012, 06:53:32 PM »

Oops can a mod move this into the engine swaps section?

suhinaffy · « **Reply #2 on:** August 10, 2012, 07:23:33 AM »

Thanks for all the help.

keflaman · « **Reply #3 on:** August 10, 2012, 10:26:11 AM »

Things move kind of slow on this board and a lot of folks with the majority of corporate knowledge have moved on and don't frequent the site as much any more.

Plus, your posts may have gotten hung up in the spam filter, so just be patient.

I will add to that the fuel tanks and lines are different between the two cars. The M20 uses two pumps and the M42 uses one pump with a pipe crossfeed between the "two halves" so to speak. You'll understand what I mean by comparing the bottom of the two tanks . IIRC you need to swap the fuel gauge for whichever tank you decide to go with and the correct coding plug on the back of the intrument panel.

NO717 · « **Reply #4 on:** August 23, 2012, 02:13:14 PM »

you will want to either swap the whole gauge cluster from the 318 to the 325. Techcinally you only need the coding plug. But swapping the whole thing is just as much work as swaping the coding plug.

DesktopDave · « **Reply #5 on:** August 23, 2012, 03:56:56 PM »

I popped you over the the 'swaps' section. Sorry...missed the original post.

I'd think you'd need the engine, tranny, associated subframe, likely the drive shaft. You won't need the diff - they're swappable. You might need to fab up some mounts as well - coil packs, maybe the O2 connector bracket. Radiator will be different. A/C and P/S if fitted are likely different units.

Other than that, I'd figure it for a nice straightforward swap. I'm looking forward to some pictures, if you don't mind and get a chance.

wazzu70 · « **Reply #6 on:** August 24, 2012, 04:09:27 PM »

I have actually done this swap! My M20 died and I wanted a more fuel efficient high revving motor

It sounds like you are on the right track with the swap.

I did not make any adjustments to the fuel tank. I used the M42 radiator assembly, and I used a coil on plug conversion for spark since the bracket for M42 coils was missing on my shock tower.

I used the M20 front subframe and trans mount.

One thing you may want to change out is the rear gear ratio. What you have will probably be better for fuel economy though.

Hope that helps. Overall it was very straight forward.

keflaman · « **Reply #7 on:** August 25, 2012, 08:05:52 AM »

Quote from: wazzu70;115162

It sounds like you are on the right track with the swap.

I did not make any adjustments to the fuel tank.

Doh! I made my comment regarding the gas tanks thinking he was swapping them between the chassis as well. Sorry for the confusion.

suhinaffy · « **Reply #8 on:** September 20, 2012, 12:55:53 PM »

Thanks for all of the input so far. I've got the m42 in and on the mounts but it's as far as i've gotten. The m20b25 went into the 318is shell and will hopefully be finished soon.

Some pics of the E30s after swapping engines...

Still some wotk to do on the IS

The m42 touring,

Still some work to do here too...

At present we are working on getting the m20 engined IS up and running as a bit of a sleeper. currently has the original is diff so we're hoping it'll be a bit quicker...

DesktopDave · « **Reply #9 on:** September 20, 2012, 07:03:28 PM »

Looks good to me. I just thought that you might need to swap the front shocks - with a lighter motor the car will sit a bit higher in the front. Having said that, the stock look on the M42 seems to be that way. Coincidentally, I have an M20 diff in mine...the 3.73. I prefer it, though it is a bit slower.