There is a noticeable weight difference between the M42 and m20 flywheels. With the clutch disc and pressure plates assembled on it, the difference is not as pronounced since the M20 uses a heavier pressure plate. The polar moment of inerta is far smaller on the M20 flywheel though. It has less mass concentrated at its outer edges than the M42 unit. This is why, despite the seemingly similar weights, the M42 with an M20 flywheel will revv far more freely.

Installation of the M20 flywheel is not a straight bolt-on. You will need a spacer ring to prevent it from contacting the back of the upper oil pan. By drilling out the 2 rivets holding the ring onto the M42 flywheel you can get the said ring. How, there is a locating sleeve in one of the holes in the back of the crankshaft. You should not go without it. The spacer does not have a larger hole to accomodate this locating sleeve. Here is where you will need to drill out one of the holes on the ring. The closest drill bit I had to the outside diameter of the sleeve was a .625" drill bit. It was a little large, but that would not be an issue. Be sure to use some cutting oil! When done, put the ring between the crankshaft and flywheel. You will also need M20 flywheel bolts. The M42 bolts are far too long for this. You will also need a Euro 323i throw out bearing for this. To complete the installation of the flywheel, you will need to lock the crankshaft/flywheel. Using an impact gun to install the bolts is a bad, and dangerous idea. The specification for these bolts calls a fastening torque of 84-92ft-lbs. I set them to 88ft-lbs. A clutch disc alignment tool is also HIGHLY recommended. Doing this without one is a real pain...I did it once.

Before reinstalling the transmission, I flushed out the fluid. The old stuff was pretty nasty. Luckily, there was not much in the way of metal debris. The new Guibo was also installed.

The final issue to be sorted out in this was in regard to the starter's pinion gear. The M20 flywheel has different starter ring tooth spacing than the M42's. You will need the pinion gear from a 1988+ 325i starter. The machining I did is unnecessary as long as you get the entire gear assembly. Make sure you have the gear, shaft and plastic planetary gear asembly all in one. If you remove the gear from the shaft, you will need to make a custom replacement for the locking ring. The part is seemingly no longer available anywhere for purchase, so make sure you take everything as one assembly!

So, there we have it. The ordeal was finally over, and I could actually enjoy the car. Being that this was the second time I had done all of this on an E30, it was not all that difficult. Knowing what to do helps out immensely. I hope that readers of this will find it useful, and that it will save them some time and trouble. Since all of this, a few things have changed. The harnesses are gone as they were almost never used. I sold the H&R springs and Bilstein shocks after breaking my oil pan on a back-road in the summer of 2006. I used some Boge TurboGas shocks and stock springs thereafter. After getting a wheel alignment, the car really did not seem to handle any worse. Perhaps it was just experience taking the "performance" parts' place. I also installed an OEM skid plate to help prevent future incidents with the oil pan. Anyone who finds this useful is welcome to email me. If you would like me to elaborate further on any portion of this, feel free to ask. I will do my best...afterall, the whole point of the site is to share knowledge!