Yeah, Benz is a whole different world, for sure!

CD manuals are available from FastLane, and usually other sources, and paper manuals (which I prefer) are often on eBay in the $100 range. Worth every penny, as many things are distincly different than standard American practice!

Look at it this way - Benz has used aluminum heads on all their gasoline engines since the 50s, and the last pushrod OHV engine they made was a diesel before WWII -- everything has been OHC (including some with jack shaft drive rather than chain drive) since the 30's. EFI since 1970, etc.

The one weak point on your 420 is the timing chain -- you MUST check the stretch (ie, wear!) every 30,000 miles and replace when it gets to 6 degrees or so, else it slaps on startup, fractures the upper guide on the right side, and the broken off part drops into the cogs, breaks the chain, and bend all the valves on both heads. About $4000 worth, more or less.

Check the stretch by removing the right valve cover and rotating the engine by hand until the notch in the thrust washer behind the cam sproket is centered around the little protrusion on the cam tower (at about 1:30, I think). Read the degree wheel on the crank pulley -- new chain will be within 2 degrees of TDC, the more wear, the later the crank will be. By 8 degrees, pull in a new chain. Check the condition of hte chain guides, at the same time -- if dark brown, replace them, they are brittle.

Otherwise, the engine should run at least 250,000 miles between valve jobs, and you shouldn't be able to wear out the bottom end -- MB used the silicon impregnated aluminum block GM developed with Reynolds for the Vega, then gave up on about the time it was perfected. Unless overheated, it should run about 2.5 million miles before it wears out of spec!

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!