Duke:

No, that is the spec. Essentially no clearance cold. If the valve spring will close the valve on assembly, it's fine. No way the VALVE is going to wear, after all! Way too hard.

The exhausts on diesels are sodium filled, too -- hence the bronze guides -- steel doesn't expand enough and they wear oversize.

A valve guide with 0.0027" clearance on an MB diesel could get replaced as out of spec. When checking, if you can feel movement sideways with the valve off the seat, the guide is shot. Very much less clearance than American practice, and if you ream them to that clearance, the engines almost always sucks oil down the guides. I know, my brother's engine had been rebuilt (badly, as some crap from the oil filter housing gasket -- excess silicone sealant, we think) plugged the oil passage to the #2 crank main bearing and caused the crank to fracture) -- not many miles on it, I don't believe, and oil ran down the valves. Very little play in the guides (steel on the exhausts), but man was there oil in the combustion chamber!

GM had fits with that Vega engine. Weird design in the first place (cast iron head on an aluminum block!), and they died at an amazing rate -- I know a number of people who got the engine replaced UNDER WARRENTY (12 month/12,000 miles in those days) due to oil consumption. The casting was a very poor design, so that piston clearance vanished on slight overheating (I think the problem was mainly no or too small a coolant passage between pairs of cylinders, but no longer remember). Get hot sitting in traffic, loose a bit of coolant, and the cylinder walls got eaten up. Certainly, the first two years or so of production all died by 30,000 miles or so. If you got a good one, they ran fine, but that was a crapshoot.

GM eventually fixed the problem, as I'm sure you noticed in the Cosworth, but abandoned the technology about the same time. Rover bought the Buick V8 version and still make it.

Typical GM -- always going rotten just about the time it should be getting ripe. There is a reason GM didn't make money building cars from about 1976 to somewhere in the 90s, if they indeed do.

Kinda silly to just give up, since the siliconized blocks are fantastic if done right.

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!