M42 Preparation

Here's how scope creep works: after researching a lot, I decide to abandon my Megasquirt EFI project in favor of an M42 engine from a 1991 318is. As it turns out, the transmission and driveshaft from the same car can be used with little to no modification, as long as one has a shortneck differential, which most 2002s have. Since my 1600 is a super early model, she has a longneck differential. The swap to the shortneck rear suspension isn't difficult, but who would do the swap without refreshing the bushings? Then, of course, one cannot refresh rear suspension components without do the same to the front. Also, the swap to an M42 requires some consideration and possible modification to the steering components, so I should replace those too.

You see how that worked? I am now doing basically the same scope of work that I did this time last year, less the interior. What's wrong with me?

Anyway, the M42 is a great choice. I realized that, noble and cool as the Megasquirt crowd is, I found it difficult to pass up the factory research and development that went into the M42. Everything from the engine, transmission and driveshaft will be from the same donor car. Also, I won't need a special bracket to hold the A/C compressor (stay tuned on that one).

Performance-wise, the M42 is a distributorless DOHC 1.8L 4 cylinder that makes 136hp. If you group it together with its nearly identical brother, the M44, it's the last 4 cylinder that BMW made until the current line of N20 engines, which have yet to see US showrooms. The M42 is reliable, light, fuel injected, digitally ignited and easily replaceable; all the things I wanted to get out of my M10.

So here it is:

I found a deal on an engine, transmission and driveshaft for not a lot of cash locally. I had to locate a complete engine wiring harness and a slew of gaskets and vacuum hoses. I also found a great thread on www.m42club.com that explained how to simplify the mess of vacuum and coolant hoses under the intake. Apparently, the US required some throttle body preheating nonsense to warm up the engine quicker, lowering the unspent fuel emissions. While noble in intent, this meant the addition of a spaghetti bowl of coolant and vacuum lines under the intake. I followed the instructions and save myself a few hundred dollars in new parts by removing all of it.

I also replaced the input, output and gear selector shaft seals. The clutch looks good and dry, so I'll leave that for now. Oil pan seals will be done soon, too. I also have a set of Jake's M42 mounts to mate the engine to the 2002 subframe.

This was before I cleaned inside the bell housing.

And after:

According to Jake, one must grind a little from the center of the steering drag link and the bottom of the transmission to clear movement for the steering. After consulting with a local 2002/E36 guy, I decided to do all of the clearancing on the transmission. So, with a little help from Dudley and his grinder, voila.