OM-615, to woodruff key or replace timing chain? - Page 2 - PeachParts Mercedes-Benz Forum

gmog220d · #16 07-15-2015, 02:52 PM

Boy, I knew the service guys at the ABQ dealer were "special", but not that special! Thanks for your support?

All the parts folks I've dealt with are helpful, Pedro especially. My only brush with the service department was the windshield seal I had them replace in a W123 300CD. They butchered the trim! And and I spoke with the "tech" before having them do the work, to make sure they knew how to deal with the pull seal and trim, and was assured it would be done properly . . . . .

I've got a fuel line cut and bent for a dripper. Lemme know if you want to come down to ABQ for that job, Phil.

funola · #17 07-15-2015, 03:59 PM

Not sure if this timing specs from the Tech data manual helps. It shows a "13" camshaft for the 115.954 engine. Is it possible the "13" was misread as an "18"?

Quote:

Originally Posted by Phil_F_NM

Ok folks, so gmog220d (Greg) helped me out a ton the other day. We got a few things sussed out: oil change, valve adjustment, checking timing with the 2mm method, pulling out my cam gear to see the offset key and were finally left with the question of what is a #18 camshaft? More specifically, we couldn't find the cam timing specs for the #18 camshaft, which is what my engine has on it. From the tag on the block, it looks like it is a Mercedes-Benz rebuild.

Things I thought I knew before working at Greg's shop:
-The timing chain was stretched about 5 degrees using the camshaft notch/tower notch against the crank.
-The IP definitely needs timing.

After the work:
-I have a camshaft with 18 stamped in the back.
-18 is not listed for cam timing specs.
-Against the 2mm valve test, my crankshaft balancer reads 16~17 degrees.
-Cam gear wear is very minimal. Teeth look good. Chain looks good.
-I have what we think is a 2deg offset key installed right now.
-My IP was missing the overflow banjo bolt/drain tube.
-I really should replace my front main seal...

Now, do any of you folks with the super secret Mercedes knowledge have the timing specs on that #18 camshaft?

Thanks all!

Phil Forrest

Stretch · #18 07-15-2015, 05:07 PM

Prompted by funola's contribution I had a quick look in the German language version of the W123 FSM and found the answer

funola · #19 07-15-2015, 05:20 PM

Good on you Stretch!

Stretch · #20 07-15-2015, 05:23 PM

Better late than never I suppose (should have checked earlier and saved parts guy encounter from happening)

gmog220d · #21 07-15-2015, 06:42 PM

Thanks Stretch! Now we're in business.

Pretty sure that we saw an "18" in there, funola. Looks like code "13" has the same specs, though.

Phil_F_NM · #22 08-31-2015, 02:17 AM

Greg, thnaks for telling me the answer was in my thread, today.
I haven't checked this thread in over a month as Bethanne and I have been moving then moving then moving again (landlord, et al difficulties.)
Anyway, back in July on the 15th we were in an area withzero cell reception and hadn't gotten our internet set up so I just didn't see the reply.
Anyway, thanks Stretch and funola!
I've decided since I'm pretty broke, just moved into a new place, saving up for a second set of wheels for some snow tires, saqving up for snow tires and having to get my main camera shutter replaced, I'm going to take the risk of sticking in an offset key and praying I get at least through the winter. The chain wasn't badly worn, the gear teeth looked good, so I should be ok. I also figure if something catastrophic is going to happen, it's going to happen. Ouch. Yes, the new chain is a bit of extra insurance but it's 10X the price of a key and quite a bit more work.
We'll get the key in there, time the IP then I'll get that linkage readjusted for altitude.

Then I'm going to attempt to use this car as my winter vehicle up in the northern New Mexico mountains. It's al we've got and it's all we can afford. She's made it so far through some really bad winters all across the country, I think she can handle it.

Thanks all!
Phil Forrest

Stretch · #23 08-31-2015, 04:18 AM

Quote:

Originally Posted by Phil_F_NM

Greg, thnaks for telling me the answer was in my thread, today.
I haven't checked this thread in over a month as Bethanne and I have been moving then moving then moving again (landlord, et al difficulties.)
Anyway, back in July on the 15th we were in an area withzero cell reception and hadn't gotten our internet set up so I just didn't see the reply.
Anyway, thanks Stretch and funola!
I've decided since I'm pretty broke, just moved into a new place, saving up for a second set of wheels for some snow tires, saqving up for snow tires and having to get my main camera shutter replaced, I'm going to take the risk of sticking in an offset key and praying I get at least through the winter. The chain wasn't badly worn, the gear teeth looked good, so I should be ok. I also figure if something catastrophic is going to happen, it's going to happen. Ouch. Yes, the new chain is a bit of extra insurance but it's 10X the price of a key and quite a bit more work.
We'll get the key in there, time the IP then I'll get that linkage readjusted for altitude.

Then I'm going to attempt to use this car as my winter vehicle up in the northern New Mexico mountains. It's al we've got and it's all we can afford. She's made it so far through some really bad winters all across the country, I think she can handle it.

Thanks all!
Phil Forrest

If your 2mm lift tests consistently read 16 to 17 degrees then I wouldn't bother with the offset key.

For the #18 camshaft that's the expected wear after 20,000km - as far as the elongation is concerned "that's a pretty new chain".

Furthermore - according to my boredom a few winters back - when I measured the camshaft profile in my OM617 and other daft things - I reckon the lower valve offset keys don't adjust for what they are meant to adjust!

See =>

OM617 (non turbo) cam profile specs, piston height specs etc

(if you want)

gmog220d · #24 08-31-2015, 10:13 AM

Phil, no sweat on the heads up. Sorry I couldn't check it for you right then as we were in the middle of packing boxes and moving stuff into storage in preparation for our upcoming move.

I really didn't take a close look at the data or give this any thought after Stretch posted his copy of the chart. Indeed, it appears that 16 ~ 17 degrees at the crank on the 2mm test would be just in spec, as Stretch has pointed out. The 2 degree (at cam) key would improve your cam timing a bit, and wouldn't be a total waste of time, perhaps. But also can see how leaving it as-is would be fine.

Why are the specified ranges so much larger for this group of cams?

Stretch, I am curious to hear more about how the smaller offset keys don't actually adjust how we want them to. When I went through this on the '74 the cam timing was behind the outer spec by about 3.5 degrees at the crank. I installed the 2 degree (at cam) key and it brought cam timing up about 4 degrees (at crank), to just within the specified range.

leathermang · #25 08-31-2015, 10:35 AM

That is wrong... you can not compare gas engines to our diesels on some factors... and this is one of the most important.. it is the reason our engines are so efficient ... gas engine users change the valve overlap when they want more power... wasting fuel in exchange for more complete exchanging of the gas air in the cylinder during the compression stroke. By definition our engines relationships are determined by the IP rpm curve built into the IP.
And OTHERS.... NOTE the threads in my signature with regard to timing.

Quote:

Originally Posted by BillGrissom

Re racing, I would think retarding the valve timing would give more power at high rpm, since that is true in gasoline engines, and it is the same issue of getting max air charge into the cylinder. Gas engine "timing sets" often have 3 or 7 keyways so one can pick an advance or retard from the "straight up" design. Advance gives better low rpm performance (torque) and mileage. Drag racers go w/ the retarded settings. They don't care about low rpm because they rev the engines at the starting line and release the brake, or slam the tranny in (sometimes explodes). I had a friend who drag raced a Pinto and would retard the timing (rubber belt) one tooth before racing.

Re an offset Woodruff key, I see no issue using one as long as the chain isn't so worn that the teeth aren't meshing correctly. If you ever fooled with bicycles, you know you need a new chain when it only contacts the first teeth and is slack behind. Too worn and the chain starts skipping on the front sprocket. Otherwise, there is already plenty of slack in the timing chain, so as long as the tensioner can keep it tight on the return side, there should be no problem.

I am fooling with this currently, and trying to get a good measurement with my dial indicator. Last time I checked my 1984, it had 2 deg crank retard, which is the factory 10,000 mi wear-in spec, but I recall using the marks to measure that (inexact). I replaced my tensioner chain because the original was riding cocked (contact circles ~1/2 off) and the rubber liner appeared hard & cracked when I removed it.

Stretch · #26 08-31-2015, 11:33 AM

Quote:

Originally Posted by gmog220d

...
Why are the specified ranges so much larger for this group of cams?

I'm not sure but I assume that's because of the influence of the development of the OM617 turbo. The second generation non turbo OM617s were upgraded with "some of the lessons learned" from the turbo development - I guess the cam profiles were from that era.

Quote:

Originally Posted by gmog220d

...

Stretch, I am curious to hear more about how the smaller offset keys don't actually adjust how we want them to. When I went through this on the '74 the cam timing was behind the outer spec by about 3.5 degrees at the crank. I installed the 2 degree (at cam) key and it brought cam timing up about 4 degrees (at crank), to just within the specified range.

Finally discussion!

I've been wondering about these offset keys for years. As explained above I did some measurements for myself a few years back (when I was really bored). The FSM gives the offset value in terms of mm and degrees. According to my measurements I got the impression that the smallest key did a better job at adjusting 6 degrees instead of four (at the camshaft)...

...I didn't get so bored as to go and buy an offset key - measure the offset in mm and then check the measurements and calculations I had made...

...you see I'm only about 80% geek! Should have gone the extra 20% just to see.

I must say your report does give me a little bit more confidence in these keys. I wonder how many people re-perform the 2mm lift test after fitting an offset key though - that would seem like a pretty good working practice! (Especially as I've heard of people putting them in the wrong way round)

Phil_F_NM · #27 08-31-2015, 11:35 AM

Interesting to look into it now that I'm awake and see that the chain is still within spec, though just on the edge.
Although I already have an offset key with a very small offset. Maybe 2 degrees?
So, no offset key to take up that stretch just do the IP timing? Although it's on the edge of being within spec, wouldn't accounting for a few more degrees of stretch make some sense?

Again, thanks to all for your advice!
Phil Forrest

gmog220d · #28 08-31-2015, 12:32 PM

Phil, I've got a 4 degree (at cam) key that we could compare yours to to get an idea of what its offset is.

Stretch, yes I did check the cam timing again via 2mm test after installing the offset key. I also noted observations of the crank in relation the cam tower marks before and after the key was installed. All my measurements/observations indicated that I did indeed get maybe a hair on the plus side of 4 degrees at the crank from the 2 degree (at cam) offset key (~ 17 degrees went to ~ 13 degrees 2mm test, and 4 ~ 5 degrees by the cam tower marks method went to ~ 0). So my cam timing actually ended up slightly in the "new" chain range. Should be good for a while yet, and next time I'll just replace the chain. This particular engine is a 616.916 with cam 06. And my notes indicate I used 13.5 degrees as the benchmark.

I find it good practice to take measurements at least twice to ensure consistent readings. If the two measurements are not consistent I'll repeat until I get a feel for the average.