I have an 82 300SD and was wondering if it is possible to measure the timing chain stretch in degrees without going to an MB dealership. Is it possible to do in my garage? Any hints, tips, insights and experiences are welcome. Thanks.

------------------
Dave.
82 300SD

Measuring is as simple as having the tools, the specs, and the technique.

You will need a magnetic or clampable dial indicator with a long probe. This should be positioned and tentioned over the valve to read verticle movement. All of the valve lash should be adjusted out, till the valve is depressed.

With your dial indicator zero'ed rotate the engine by the crank bolt in the direction of rotation till there is 2.0mm of valve movement (intake valve). Look at the crankshaft balancer and read the degrees off the wheel next to the pointer.

The deg should be 9 ATDC with new chain and 11 for chains of 20000km. This spec is for the cam with #11 stamped in the rear journal.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

What is the number of degrees as measured above when a chain is worn and should be replaced? I couldn't find any wear limit in the MB manual.

------------------

MB has never given such info. These measurements are seldom made in the modern shop. MB made provision for correcting this value through offset keys so there is never any reason why that cam timing can't be achieved no matter what the chain stretch.

I would guess that a chain with 3-5 deg of stretch should be replaced, BUT, there are other factors that change the cam timing including the decking of the block and either side of the head also cam or follower wear.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks all.
I guess all I have to do now is find a dial indicator. Hmmmm, I wonder if I could use my verniers instead...just a thought.

Dial indicator is the acurate way, but for a quick check, there is an indicator line and notch at the front of the cam that, when aligned, TDC will show on the crank damper . If these don't coincide, the chain is streched.

I have done the quick method many times with good results. If the lines are perfectly aligned, any more than 3 degrees should be replaced.

------------------
Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

That does sound easier. I'll give that a shot and if it looks to be out I'll measure it more accurately. Thanks to all who have posted.