The 2nd generation M30’s primarily came from the E23, E24, and E28 body-styles. These engines are from 1983 to 1987. These engines typically put down around 207hp. These engines require an oil pan from the 3rd generation M30’s to clear the steering rack. This write-up mainly discusses the 3rd generation M30’s, but the differences are highlighted here.
The 3rd generation M30 engines are more efficient and generally produce more power. This engine was used in the E32 and E34 models and produces around 211hp. This model is more aesthetically pleasing in the engine bay, with more cowls, plastic covers…etc, but it is simply more modern, using Motonic 1.1. Turbo-charging this engine, even though it has a higher compression ratio than its predecessor, is still an excellent option. As a note to adding a turbo to a completely stock M30, keep the psi around 7-8psi or you’ll blow your head-gasket.
For a generalization of the M30 years,
M30B30 - Introduced in 1986 with the E32, the 2.9 L (2986 cc) M30B30 produced 185 hp. The engine continued in production until 1993.
1986-1992 E32 7-Series
1988-1993 E34 5-Series
1985-1988 E28 5-Series
1985-1987 E24 6-Series
1985-1987 E23 7-Series
3.4 liter (3430 cc) SOHC inline-6 cylinder
9.0:1 compression ratio
208 hp @ 5700 rpm w/ catalytic converter (~220 w/o it)
225 ft•lbf torque @ 4000 rpm
89 Octane fuel or better recommended.
1988-1989 E24 635CSi
1988-1993 E34 535i
1988-1992 E32 735i
To re-iterate, I highly recommend obtaining an engine from an E32 or E34. They’re just as cheap as the 2nd generation M30’s and it’s more compatible electronically to the E30’s. As you read through this guide, you will find that using these engines are better in almost every possible way. A quick run-through of why they are ideal for this swap.
The electrical hooks up virtually perfect with your car (assuming your donor car is ‘88 - ‘91 E30). A donor car from ’84-87 is not much different, just some minor wiring modifications. The 318i, which has a rectangular C101 port will require more modifications, but this would have to occur no matter which M30 you choose to swap.
The oil pan and pump do not need to be modified at all for this setup. It will clear the steering rack without issues.
It is more efficient as it is the latest generation of M30 motors
It is much more eye pleasing in the engine bay. i.e. more covers/cowls.
It is more technologically advanced and more reliable than an engine from an E23 or E28 or E24 735i or 535i or 635csi respectively.
It is not impossible at all to do the conversion with any E23, E28, or E24 motor, just complicates it some…notably, electrical, and oil pan. This will be covered only briefly as I never performed this in my swap.