My 380 SE is approaching 100,000 miles and I think I may want to tackle the replacement of the cam chain tensioner and guide rails. There are a few excellent sites which detail the process, and after studying everything, it does not seem impossible if I am patient and organized. The only tough part of the process (from what I can see) is the removal of the distributor on order to get at the pins which hold one of the guides in place on the driver's side bank of cylinders. The engine is at TDC, the cap and wires are removed, is it only one 13mm bolt that holds the dirstibutor in place? Will the distributor shaft only go in one way (the right way) upon reassembly?

I would hate to get 3/4 the way through and get stuck at this point.

Anyone have experiance with this?

Thanks in advance,

John

See Picture 31.

You can replace it incorrectly as it rotates in on a spiral geared shaft, but there's only so many ways you can do it.

Before removing the rotor arm, align the passenger side cam at top dead center (mark behind sprocket aligned with cam tower by rotating engine with a 27mm socket at the crankshaft) and your rotor arm should point to the cast mark on the distributor housing - Picture 13. If in doubt, turn the rotor arm counter-clockwise to a stop (no force needed). It rotates clockwise when running, so you will be removing the few degrees of lash these have. Note the position of the rotor arm with respect to the housing and, if in doubt, use a felt tip pen to mark the housing where the 'sharp' end of the rotor arm resides.

It's retained by just the one 13mm bolt.

If your 380 uses a single row chain, consider replacement to a double row as the single has a troubled, and short, life.

If you put the shaft in wrong, you will see it comes to rest way out of alignment. Don't sweat a degree or two as the electronic ignition allows for that. Indeed, although the 13mm bolts is in a slot which permits quite a few degrees of rotation, just about any position should work in my experience thanks to the electronic timing.

One other thought - my experience with the timing not being adjustable is on a 1990 560SEL; as I recall the timing on my wife's 1981 380SLC is adjustable, so the change was made some time in between - it may be that yours is adjustable so I suggest you check with those expert in the design for your year. Sorry if I mislead you. The pivot pin locations and their removal is probably similar to what I illustrated on my site

Thanks a million for the info, and especially for your site. I actually printed off all the photos and will try to use them when I do the job. I am substituting a beagle though.

My camchain is double row, but I have another question.

Did you install the cam chain tensioner on the passenger side before you started work on the driver's side? It would seem to me that you would need all the slack you could get, but perhaps I am wrong. Would the driver's side of the camchaiin not be quite tight if the tensioner was in?

John -

I installed the new tensioner before commencing work on the driver's side; my concern was that all that loose chain flopping about might skip a cog and I would miss it. I suppose the fail safe is to mark the chain and cam gear on the passenger side with white paint to keep things properly referenced in the event this happens, should you prefer to leave the tensioner out. The 117 engine (yours is a 116 but pretty similar if my wife's 380SLC is anything to go by) factory manual is silent on this.

The increased chain tension from the new tensioner was not an impediment in practice as I found turning the driver's side cam a tad to secure alignment of the Woodruff key with the slot in the gear when replacing the latter needed little force using an 'English' wrench (the adjustable bodger's special).

One last thing - do check the part numbers before ordering as I am unsure whether the chain rails in the 380 are the same parts as those in the 560. My total parts cost was under $125. Labor was free but my Border Terrier charged me 2 cookies in exchange for moral support.

A beagle should work fine!