Actually, it's even more tricky that that -- the silicon is actually precipetated out of the melt around the cylinder bores, so the concentration is very high.

The porous silicon wall will last essentially forever if you don't overheat the engine -- should wear at 1/5 the rate of cast iron, and the iron version of this engine (M116 and M117) usually run 500,000 miles without bottom end work.

Nice car.

Watch the timing chain stretch (hopefully someone swapped the single row chain for the double row). You need to have it checked EVERY oil change, chain must be replaced if significantly "stretched" (actually, worn). Otherwise, they break, and you will be doing another valve job.

Otherwise, a standard W107 or W126 depending on what you have -- there is, to be best of my knowledge, no SC style. Either SL, SEC (coupe) or SEL, large sedan.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!