Timing chain stretch measurement/specifications (confused)
 

Could anyone please kindly look up some information for me?

I'm trying to accurately check the timing chain stretch because the car has 204,000 miles on it & I don't know if the previous owner (the proverbial little old lady from Pasadena) ever had the chain replaced. When I measured using the crude method of looking at the alignment marks, it lines up perfectly. It just seems too good to be true at this mileage, so…

This weekend I checked the amount of timing chain stretch using the dial gauge method. What I came up with was a measurement of 22 degrees BTDC (measured at the crankshaft) at 2 millimeters of valve lift on the intake valve. I rotated the engine through four complete cycles and came up with the same result each time. (Yes, I did remove all valve lash prior to making the measurement.)

According to the service CD as well as prior posts here, specifications call for 11 degrees. This of course *would* equate to 22 degrees at the crankshaft, but unless I'm mistaken the specification calls for 11 degrees *at* the crankshaft. Can anyone confirm what the proper specs are for this car? It is a 1984 300D, California version. It seems pretty far-fetched, but does the California version have a different camshaft than the Federal cars? (To meet pollution regs?)

ANY input from you guys out there in cyberspace is greatly appreciated, as always!

RTH

The descrepency between perfect installation mark alignment and 11 degrees off with dial indicator test is just too great.

I expect that there is something amiss with the particular spec. you are using. You could very well be right about a California being that much different, but I don't expect that to be the case. Camshaft profile on a diesel should have little or nothing to do with emissions.

As far as the perfect alignment of the installation marks at 204,000 miles, I don't find that hard to believe at all. Even my daughter's engine that turned out to be poorly cared for with worn out cylinders had perfect installation mark alignment.

These cars have a double row timing chain that you could use to lift a battleship. I doubt that you have any stretch at all unless the PO rarely changed the oil.

The failure of the timing chain in these cars is much more often attributed to low oil pressure which renders the tensioner less than effective, or broken guides.

I hope you can find the exact information so you can use the dial indicator to put your mind at ease.

Good luck,