Engine Swap - M42

The four-cylinder engines get a lot of stick from E30 owners. "Feeble", "weak" and "two pistons short" are the usual complaints made against the rattly M10 and its M40 sibling. And while it's true that the four-pots can feel a bit asthmatic after driving a big six-cylinder M20, it's not true that all four-pot engines are rubbish; after all, the M3 was powered by the four-cylinder S14 lump.

If you want more poke from your 318i without the drinking problems inherent of the bigger engines, then look no further than the M42 engine. This fizzy little four-banger features the same 1.8 litre displacement as the other E30 engines, but with double the valves (16 in all) to crank the power up to 140bhp. Combined with a simple drop-in swap procedure and easy-to-find spares from the E36, the M42 swap is a great way to liven up the smaller-engined E30 models.

Identification

The M42 engine is found in two cars; the 318is versions of the E30 and E36. However, the E36 318is was later "upgraded" to the M44 engine, which is not as desirable for a simple swap due to its increased complexity. To make sure you're getting the right engine from a donor, the most obvious way to identify an M44 engine is by the crank sensor being at the rear of the block, not the front timing case:

M44 crank sensor location:

M42 crank sensor location: