Does anyone know the correct timing for a 1988420SEL. Also is that for the Car in Drive or neutral. Thanks!

These engines do not have an adjustment. The distributor is adjustable, but it will not affect the timing in any way. The timing is set off of the crank sensor. If you move the distributor, you will make things worse, not better because you will be opening the rotor gap.

I have heard that it is possible to check for chain stretch in these cars (420SELs - mine is an 86) by measuring how far off the cam timing is. How is this done? Is it hard, and can my mechanic do it quickly. I am curious because I know chains in these engines need to be replaced every 100,000 miles. I'm past 180,000 now, and although I have no record of a chain change in the records that came with the car I'm sure it must have been done. I am just wondering how much longer before I need to change it. Also, if the timing is retarded due to chain stretch, what kind of other benefits will I see, other than avoiding a major catastrophy (better mileage, more power?).

No Timing
 

Thanks for your answer Benzmac! However need to know the Ga Gap spacing. Had to change waterpump and of course that means lifting up the Distributor to get to the bolt. It may be off a little. Any help? Thanks,

Ed.

420SEL, (Jason), in reply to your question about timing chain stretch:

Remove both valve covers and rotate the engine until the crank pointer is on '0'. Observe the timing marks on each camshaft, and their relation to the mark on each cam bearing tower. If all is well, the marks will be aligned. The stretch in the chain will be illustrated by the misalignment of these marks.

I would worry more about the plastic rails in the heads than the chain. These fail from exposure to heat in the engine, and become brittle. They break and fall between the timing chain and the crankshaft sprocket, causing the engine to jump time. Pistons hitting valves, cats and dogs living together, its all bad! I changed my guide rails and chain at 125K miles and thought I had cheated fate long enough! At 180k, I would be thinking about it seriously.

In response to what improvements in engine performance: I thought mine ran smoother afterward, but that may be my imagination, as we all like to think after a weekend under the hood things are ALWAYS much better! But I did not have much stretch observed before the job.

Do a search on timing chain, and chain guides. There is plenty of info on that here.
My $.02 worth on this.
Good luck!