I recently acquired an interesting 2002 here in Austin. It’s an M20 six cylinder engined car with an e30 5-speed. It was converted to six cylinders in the mid-’80s by an Austin engineer—not a professional BMW technician, but someone with very high standards, a solid mechanical engineering background, and great aptitude. Now, 35 years later, we know how this change “is usually done”, but back then this engine swap was highly unusual and he had to make everything up without internet help. As an aside, do you know about SAAB cars? SAAB was principally an aircraft manufacturer at one time and when they decided to make cars, they didn’t need no stinkin’ advice about how other people made them. They did it their way! This 2002 has some of the same kind of thinking behind it!
First of all, the six cylinder engine is longer, of course, and these days we make the engine compartment longer by moving the radiator further forward. This car doesn’t have that change. Our engineer seemed to think that the radiator core support was inviolable and he did not cut the core support to make more room. He did install a thicker radiator to handle the additional engine heat, but he modified it by cutting out a section in the center of the core to make room for the water pump snout! Similarly, he found that the Motronic distributor cap at the front of the cylinder head was too close to the radiator. To deal with that problem, he found a distributor from a Euro 323I M20 engine which mounts on the side of the block. He deactivated the centrifugal advance mechanism inside the distributor and just stuck it in place. The engine still runs with Motronic spark control—the computer doesn’t care very much where the distributor is placed. No timing adjustment is needed. Figuring this out was a big leap—very clever.
Another engineering milestone he faced was the driveshaft connection to the transmission, These days we just shorten the driveshaft as needed and weld on the proper flange to mate to the flex disc at the transmission. Our engineer didn’t know to do that. Instead he had a machine shop make him a steel block that bolts to the transmission output flange and accepts the 6 bolts of an e30 rear axle CV joint. The CV is attached to half an axle shaft which is welded to a ONE-PIECE driveshaft! Very inventive!
These are the highlights. He also had to make motor mounts, trans mounts, trans crossmember, fit the exhaust, fit the thicker radiator, etc. Additionally, he used a 2.7 liter eta engine with a modified cylinder head to allow the use of the higher revving “i”-camshaft. He did a lot of other work—Bilsteins, lowering springs, bigger sway bars, Recaro seats, tii struts, and more. He did a bunch of work with bigger brakes before settling on vented front rotors with e12 calipers, and larger 320i rear shoes and drums. The DUAL front calipers on each wheel that he ran for a while turned out to be too much, even for him.