I have read through many posts related to chain stretch, and installing an off-set key on cam shaft for timing gear to compensate for chain stretch. I recently put in a new timing chain at 250,000 miles. The old chain was original since the car was new, so no one previously installed an off set key...my question is this...

Since the timing chain is new, does that mean that I don't need to check cam timing? E.g. does a new timing chain automatically eliminate the need for an off set key, or do I still need to check this?

(My engine is running rough, and I am going through the process of checking many things....injectors, compression, clean fuel delivery valves on injection pump, checking injection pump timing, etc..etc.....)

Thanks,

Mark

__________________
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Timing needs to be checked. Installing a new chain does not automatically mean its reset to 0.

Did you replace the chain only or the guides as well? It's more important to change the guides than the chain.

In theory, if the chain is manufactured properly, the distance between the crankshaft and the camshaft is perfect and there will be no retardation of the camshaft. In reality, the timing might deviate slightly due to tolerances in the chain and wear in both the crankshaft and camshaft sprockets.

However, the amount of the error will not be large and for an accurate measurement, you'd need to use the 2mm valve lift method to check the cam...............something that most folks are not equipped to do.