This 325CI came to me with rod knock and a bad crank journal. Instead of rebuilding the 2.5, I swapped in an M54B30 out of an X5, swapped the oil pan and MAF over, and reprogrammed the car for the 3.0 so it runs like it was born with it.

The donor was a clean local 3.0 with about 140k, checked before install: no sludge, no glitter in the oil. While the engine was out I did everything you never want to pay labor on twice: all new seals, rebuilt the VANOS, new timing chain guides, new flywheel and clutch, water pump, and the rest of the maintenance items. The oil pump nut got safety-wired, a known M54 failure point. The point of doing a swap right is that when it goes back together, nothing is left waiting to leak or fail next season.

Read the full write-up: how the swap decisions got made →