Gypmpie:

You should have a dual action vacuum advance on your car, unless you have fuel injection.

The proper correction for high altitude is to put leaner jets in the carb (actually larger air tubes in the Solex, I think). Timing should stay the same, you need to correct for the difference in air density to keep the fuel mixture correct. If you plan to drive at low altidude out here in the flatlands, you will need to put the originals back in or you will run rich -- another argument for fuel injection.....!

To check chain stretch: Remove valve cover. Set engine to TDC on the #1 compression stroke (both intake and exhause valve cam lobes pointing up) by matching the mark in the cam with the mark on the tower. You can use either cam -- exhaust side will be slightly later than intake side. Then read the degrees off the crank pulley.

You must, of course, rotate engine in direction of normal travel using the crank pulley bolt, and stop when the cams are lined up, not the crank indicator. It won't match at TDC, the difference at the crank is what you need to check. Make sure chain tenstioner is tight, too.

Less than 4 degrees is fine, 4-8 you need to plan on a new chain, more than 8 get it outa there soon!.

Valve timing can be set with offset Woodruff keys (the little semicircular thing that keys the cam gear to the cam) -- they are available in 2 degree increments up to 10 or 12 degrees (although I would only use 4 degrees -- more than that, replacing the chains makes more sense).

And yes, incorrect valve timing will cause low vac and running problems -- basically a late cam requires more rpm to deliver the same power. Eventually, wear will make the cams so late you loose power.

Peter

__________________
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!