Hi Rob,
I went ahead and installed the 5-degree offset key on the '79 SD. That put the cam timing mark just ahead of the mark on the cam tower. A little advanced on the cam doesn't hurt anything (usually helps performance), and I won't have to worry about cam timing again on this engine.
After doing so, everything improved: performance, fuel mileage, starting, etc. Much livelier off the line. This was done at 328K miles. It now has 345K.
On the engine going into the Jeep, while the car it came out of was reading 245K miles, the engine was a factory remanufactured one, and maybe had 50K on it. The 3-degree key got the marks lined up nicely.
Timing was measured using the timing marks at both the crankshaft and the camshaft. Not the best, preferred way, I know, but past experience using a degree wheel and dial indicator on this era of MB engines has shown that German precision extends to the placement of the timing marks, and then it's up to the patience and eye of the person doing the degree-ing. Even when I degreed American V-8s back in the day, the marks were usually not more than a degree off.
Certainly, the longer the timing chain, the more stretch and camshaft mistiming can be expected. Yet another reason to recommend flatheads and "underhead" cam engines with camshafts that are gear-driven (like Stove-bolts, Harleys, the V-4s used in old SAABS, my BSA Rocket 3, et al.)
Mark in Centennial, CO
On August 4, 2019 at 1:53 PM "Aleph93 aleph93@ca.rr.com [diesel_mercedes]" <diesel_mercedes@yahoogroups.com> wrote:
Thanks Mark (s).
I did a bunch of forum reading on timing chains, and feel I have some time to figure out what to do.
A few noticeable points I found, many folks said that using the cam marks to find the stretch isn't accurate enough, there's a more involved test measuring the cams, where someone else posted, if you're going to spend the time to measure it, you should just replace the chain.
On yours, how far off was it, and which offset woodruff key did you use? (I'm assuming 5* off, get 5* offset key)
Was it measured by the cam marks? Did the fix work? noticeable difference?
*The stretch maximum seems to differ on each engine, the 617 can stretch a bit more. Some said that the chains are made to stretch into 2* off by the factory. Right about the FIP.
At least I have time to think about it.
Thanks
Rob
==
I'll save all this info, and
On 8/4/19 9:06 AM, MARK BRAUER beeser@comcast.net [diesel_mercedes] wrote:Timing chains do most of their stretching at the beginning of their lives, something like 85% of the total possible stretching in the first 70,000 miles. From there, most of the timing changes are due to the wear of the gears as the chain embeds into them. I doubt there's much stretching at all after 150,000 miles.
Mark in Centennial, CO
On August 3, 2019 at 11:28 AM "Aleph93 aleph93@ca.rr.com [diesel_mercedes]" <diesel_mercedes@yahoogroups.com> wrote:
Mark (s),
Yes, Kent alluded to those offset woodruff keys in his video, maybe that would be a good next step, and worry about the chain later, when it stretches more. I get some smoking, which I feel that I shouldn't have, with my rebuilt turbo, rebuilt injectors, clean fuel system etc, maybe the timing will help. If MB makes a 5* offset woodruff key, then it seems like it's within spec to use.
How long do timing chains last? (I know, it depends) Do timing chains stretch evenly throughout their life, or do they stretch more near the end? I don't want to have a catastrophic failure of the chain.
My '85 300D now has 232,000 miles on it.
I bought this car in 2005 with 93,000 miles, and have kept up the maintenance schedules for the 140k that I've owned it.
If I keep at my current usage, it'll be around 300K in 7yrs (2026), and if the chain stretch rate is even, it'll be about 7* off by then, w/o offset woodruff key, 2* off with the 5* key.
Thanks
Rob
On 8/2/19 8:28 PM, MARK BRAUER beeser@comcast.net [diesel_mercedes] wrote:I bought a new timing chain years ago, but never installed it. Instead, I decided to install an offset woodruff key at the cam gear:
Greatly saved the time and trouble it takes to replace the chain, which will eventually stretch anyway. By using the offset key, I can retain my broken-in/pre-stretched chain, and keep proper cam timing, probably indefinitely. And, because the keys are available in 1-degree increments from 2- to 5-degree offsets, you can set the cam timing to within a gnat's ass.
Mark in Centennial, CO
On August 2, 2019 at 5:45 PM "Aleph93 aleph93@ca.rr.com [diesel_mercedes]" <diesel_mercedes@yahoogroups.com> wrote:
Kinda quiet on our MB e-list.
I finally got some time to do the MB 15K service on my '85 300D: Oil
change, all filters, adjust valves, check timing chain, and a diesel purge.
The valves were spot on, so just a check no adjustment, the timing chain
was 5* off, which can start causing timing issues, though not an
emergency according to Kent at Mercedes Source. I'll plan to replace the
chain next year.
Anyone change a timing chain yet?
Mercedes Source has this video on how to check:
How to Check Internal Engine Timing to Determine Timing Chain Stretch
https://www.youtube.com/watch?v=k1Hlul4tIPs
I noticed the 'Accelerator Linkage Mount,' on the firewall, was loose
inside and the inner ball was crumbling, so I glued it back together for
now, and ordered a new one from FCP Euro. I called the Mb Classic
center, and heard that MB discontinued this part, though there's still
some for sale out there. If yours is questionable, you might want to
replace it.
Rob
Garden Grove
'85 300D CA
Posted by: MARK BRAUER <beeser@comcast.net>
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