offset timing keyway
offset timing keyway
Senior Member
Joined: Jun 2006
Posts: 303
Likes: 1
From: Northern California
It changes all the time
First of all that procedure is fairly difficult to explain in a thread. The procedure should be outlined in the M103 manual. That same set of offset keys has been used by Mercedes since the 50s, and is generally only used when the head has been machined. The timing chain in the M103 engine is pretty bulletproof and is usually never replaced. If you pulled the head just to do a valve job and didn't machine the head, your timing should be fine. You can even do what the machineists call kiss the head, and be just fine.The length of the chain and size the gears are engineered so that the crank position is zero and the cam is right on the mark. As a chain wears cam timing retards. After you install a new chain all the marks should line up again. If you machine they had, however, the distance has been changed. This is when you install an offset key to change the cam position a few degrees to line the marks up again.
Thread Starter
Newbie
Joined: Oct 2010
Posts: 3
Likes: 0
From: Pacific NW
91 300se,89 300se
Thank you for the clear explanation and information, I have not removed the head, I am now good to go. My brother had his head's machined on his 89 560 SEL and had told me his mechanic had used an offset key, this had me questioning if I needed it. Your reply is very appreciated, Thanks again G'Day
Senior Member
Joined: Jun 2006
Posts: 303
Likes: 1
From: Northern California
It changes all the time
You're welcome, and it sounds like your brother found a professional mechanic.There are too many guys out there that got a box of tools together, started fixing on cars, and called themselves mechanics.
Thread Starter
Newbie
Joined: Oct 2010
Posts: 3
Likes: 0
From: Pacific NW
91 300se,89 300se
Yes, his mechanic was trained at the MB factory , I was a mechanic that started with a box of tools. & early air cooled VW's, I'm 2nd owner of a 57 sunroof bug that led me into to years of turning wrenches. New to MB. Love my 300SE, Deutschland engineering look's like I'm hooked on it.
