R107 M116 cam timing mark way off
 

Hi all,

Innocently enough, I wanted to check the "stretch" on the timing chain in our'85 380SL. However, the camshaft and crankshaft timing marks aren't even in the same ballpark. The picture included here is where the camshaft timing mark is when the crankshaft is at TDC. This is the passenger's side cylinder bank (USA).

I thought maybe the harmonic balancer slipped, so to check that, I pulled the spark plug from cylinder 1, stuck a chop stick in, and watched its travel as I rotated the engine--its travel matches the markings, so no dice there.

The weird thing is the car is running fine. So I'm wondering if the marker on the camshaft is wrong? The mark is on the compensating washer--is it possible for that to get out of alignment?

According to the service manual (https://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M116_38/05-220.pdf) the intake valve is supposed to open 22 degrees ATDC, so I could verify the camshaft position that way.

Any idea what could have happened or what I can do? Thanks!

pull the other cover and look there. i always pull both, zero the crank, then turn the crank until the cam marks line up. USUALLY, it's the lh cam that's out with a stretched chain. anything to 5 degrees past crank zero is ok, 6 or more will be trouble, 8 is trouble-do it now.

curious where the cranks is when the rh cam lines up.

The right-hand camshaft has two woodruff keys; the inboard key locates the comp washer & the spacer, the outer key locates the sprocket. It is possible that the inboard key is missing or damaged, and that the comp washer has rotated on the shaft. This can be checked by loosening the sprocket bolt (counter hold the camshaft w/visegrips), and tapping the comp washer tangentially with a small punch in the notch.

Thanks for your responses! And sorry for my delayed response—my first post had to be approved and I didn't realize it had posted. I'll try and check this weekend.