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I know this is not exactly e28 turbodiesel material but I have a 535is that I love. The M30b34 is great and all but I am wanting to do something a little different than the average dood. The idea is to swap a om603 3.0 6 cylinder turbo diesel out of a Mercedes, along with a holset hx40 and upgraded dieselmeken fuel injection pump. Anyone have any clue how good it would fit and what problems I could come across in my journey? I plan on using a BMW ZF 5 speed. The goal is 400whp with some black smoke.

Are you familiar with the 603.960/.961? I have owned one in my 300SDL since 2005 and fixed a few for others over the years.

Early head castings can and do crack when overheated by previous owners, ALL 3.0L units in the US came with a No 14 casting from the factory. 15 is the first updated head I have seen and owned, 17 to 22 are for sure 3.5 heads. 22 being the most updated with the smaller oil pressure port that is the failure point of the head gasket. The 3.5L top ends swap right over BUT you must use those injectors due to different prechambers and injector angle. Also the IP lines are different. Glow plugs also differ for the 3.5 heads.

It seems early timing covers like to fail at the tensioner pivot due to the power strokes of the engine and the rapid acceleration and deceleration of the accessories on the belt drive. This is lots of fun as it can destroy the top end by jamming the chain. Hold onto your ass when you price out the most updated cover, they are around $820 with current MBCA discount. It is significantly reinforced and found on the 350SD/L and the 300SD/S350D in the W140.

Be sure to use a late vacuum up with a closed bearing. Easy to spot as the front cover has rivets to hold it on.

IMO, the W124 is a far superior chassis due to its multilink rear suspension (not to mention far better HVAC, if that matters to you) and finding an '87 with a 603 factory installed is still possible. 300D 2.5s are much more common and same motor, minus a cylinder. Just five speed swap it and get on the road. 400E brakes will bolt right up (four piston vented front, two piston vented rear, twin diaphragm booster w larger master) as will 400E sway bars. Plenty of suspension stuff around due to the 500E.

Anyway, if you need me to give you a rough length of the engine, just ask me.

I love your swap idea, its one that I've dreamed of for a long time!

If you're still working on this swap id love to hear about progress. I was going to do an om617a swap but the om603 is definitely the move. We built one for Sun Racing in association with DieselMeken for their land speed record car. 400hp on a stock motor, 300 mph. Solid motor 10/10