617 timing chain 12* to much? - Page 4 - PeachParts Mercedes-Benz Forum

winmutt · #46 04-14-2009, 04:24 PM

Quote:

Originally Posted by JonL

Yes... you should try to stop yourself from getting another infraction, and I won't say something that'll get me my first.

I finally found the DIY article on this (I never knew where those DIY's were posted before, found them under the "resources" tab. I am now confident that my analysis as posted above is 100% correct, and that the OP has chain stretch close to the limit or beyond. He is not at 12 degrees by the 2mm lift method. He's probably somewhere between 16 and 26 degrees if he were to measure with the 2mm lift method. This assumes that the accuracy of lining up the cam reference marks is +/- 5 degrees.

I know that om the om60x the notch method is supposed to be much more accurate and that on om61x is a wild assed guess. Either the washer is spun or the cam is off (per someone elses diagnosis). I don't think that anyone would let the chain stretch get that far without correction.

JonL · #47 04-14-2009, 04:52 PM

Quote:

Originally Posted by winmutt

I know that om the om60x the notch method is supposed to be much more accurate and that on om61x is a wild assed guess. Either the washer is spun or the cam is off (per someone elses diagnosis). I don't think that anyone would let the chain stretch get that far without correction.

What does "the cam is off" mean? I have no doubt that there are plenty of cars running around that have never, ever had their cam timing checked or corrected.

winmutt · #48 04-14-2009, 05:45 PM

Quote:

Originally Posted by JonL

What does "the cam is off" mean? I have no doubt that there are plenty of cars running around that have never, ever had their cam timing checked or corrected.

I'll just wait for the 2mm report

I think the washer is off or the cam is off a sprocket. I just don't buy 12* being correct. Knowing which model and some history on the issue would be extremely useful.

barry123400 · #49 04-14-2009, 05:55 PM

I did not think 12 degrees was enough for a sprocket tooth off. Kind of thought about it though during my first post.

I fortunatly have never lost a timing chain on anything personally. Several rubber timing belts though.

Having timing chains means appropiate oil changes should be a real ritual. The chains will really wear much faster with old oil than any other component in the engine I am aware of.

JonL · #50 04-14-2009, 06:06 PM

Originally I felt that the cam timing was far enough out that he ought to just replace the chain and not bother with the 2mm lift procedure until after the fact... but now I'm very curious to see where the cam timing is at with more accuracy.

81300sd · #51 04-14-2009, 09:29 PM

The washer is keyed.

Doktor Bert · #52 04-14-2009, 09:35 PM

Quote:

Originally Posted by barry123400

"I did not think 12 degrees was enough for a sprocket tooth off..."

The camshaft sprocket has 40 teeth, giving each tooth roughly a 9.0° influence on timing...Robert

jt20 · #53 04-14-2009, 10:14 PM

^^ but that is manifest as 18* at the crank when the marks are lined up on the cam.

jt20 · #54 04-14-2009, 10:15 PM

Quote:

Originally Posted by 81300sd

The washer is keyed.

but some washers have two slots..

rummur · #55 04-15-2009, 04:34 AM

I measured using the 2mm drop method.. was nearly off the scale at 30, right on the edge of the harmonic ballancer. Its probably off a tooth. Although I dont see how it got off a tooth?

rummur · #56 04-15-2009, 04:45 AM

617 016 0301 is cast into the head.. I dont know exactly what engine this is, as far as year or model car it was in.

dannym · #57 04-15-2009, 08:42 AM

Somethings not right. Did you follow the tutorial?
http://www.peachparts.com/Wikka/OM617TimingChainStretch
Did you remove valve lash before taking the measurement?
Maybe your post wasn't tight enough on the indicator?
Did you have help?

I would suggest you do it again with someone watching the dial indicator and support posts while you turn the crank around.

The reason being is even though the cam mark method isn't precise it should get you in the ball park. You got 12* with this method, there's no way you got 30* with the 2mm method if you did it right.

With the 2mm method the spec is 11.5*. If you have 12* stretch you should see 23.5* on the crank. I can see it being off by a degree or 3 but not 6 1/2.

Also note in the tutorial that using the cam aligning marks you should see 2* at the ballancer for a normal chain.
This was debated at length before being added to the tutorial.
If a reading of 12* was seen using the cam marks a 10* woodruff key will bring it back to spec.

Danny

winmutt · #58 04-15-2009, 11:34 AM

Are you sure you were at TDC?

leathermang · #59 04-15-2009, 11:38 AM

This is a great thread.

barry123400 · #60 04-15-2009, 12:03 PM

The plot thickens. At thirty degrees I would expect valve interference. So I doubt it was accurate. Some investigation may now be required to find out if a new chain was improperly installed at some point depending on what turns up.

These chains never self jump without a lot of assistance. So much so the engne will not run because of the damages. There can always be an exception of course to anything but it would be highly unlikley.