timing chain elongation curious results - PeachParts Mercedes-Benz Forum

fochs · #1 11-23-2011, 05:56 PM

I am attempting to ascertain timing chain stretch on my 83 240d. Using the cam mark reference, I get a reading of approx. 7 degrees after ot. Now it gets good. Using the 2mm method, with my dial indicator on the cap nut of #1 cylinder intake valve which is adjusted for no clearance, I consistently get a reading of 19 degrees before ot. My understanding is that viewed from the front looking down at the balancer wheel, to the left is after and to the right is before ot. According to the maintenance manual at 5-215, The chain value is nominally 11 degrees after ot. I suspect my chain cannot be elongated 30 degrees, so am I just misapprehending the values and have 8 degrees of stretch, or is something curious going on?

leathermang · #2 11-23-2011, 05:59 PM

check the ref in my sig..
there may be a constant to add or subtract... forgot which..
but throw out cam marks results..
No way it is 30 final ...
did you check to see if it has an offset key in the cam ?
Greg

Brian Carlton · #3 11-23-2011, 06:06 PM

Quote:

Originally Posted by fochs

Using the 2mm method,

............... or is something curious going on?

2mm is .080 on the dial...............

fochs · #4 11-23-2011, 06:14 PM

Greg, I have not checked for a woodruff key yet. I modified my dial indicator so that I could get it vertical to perform the test. My previous value with the indicator at an angle was about 21degrees BTDC. With the extension I fitted It was a repeatable 19 degrees BTDC. According to the maintenance manual the intake valve opens value should be at 11 degrees ATDC. Am I at the wrong side of the scale here? The cam mark value is ATDC and the 2mm is BTDC.
Eric Fochs

fochs · #5 11-23-2011, 06:18 PM

Quote:

Originally Posted by Brian Carlton

2mm is .080 on the dial...............

I read the value at .080 on the dial 8 out of 10 on the index marks. Harbor freight dial.

leathermang · #6 11-23-2011, 06:18 PM

Were we talking about checking to see if your pulley marks were accurate with respect to crank TDC ?

Brian Carlton · #7 11-23-2011, 06:21 PM

Quote:

Originally Posted by fochs

Am I at the wrong side of the scale here? The cam mark value is ATDC and the 2mm is BTDC.
Eric Fochs

Yes, you've got the interpretation of the marks reversed.

The cam mark value is BTDC and the 2mm lift method is ATDC.

Brian Carlton · #8 11-23-2011, 06:22 PM

Quote:

Originally Posted by fochs

I read the value at .080 on the dial 8 out of 10 on the index marks. Harbor freight dial.

Check.

Rules that out...........

leathermang · #9 11-23-2011, 06:22 PM

Thanks Brian....

Brian Carlton · #10 11-23-2011, 06:23 PM

Quote:

Originally Posted by leathermang

Thanks Brian....

I learned it from you.............

leathermang · #11 11-23-2011, 06:24 PM

Eric, are you just checking for fun or is their a performance problem you are experiencing ?

fochs · #12 11-23-2011, 06:30 PM

Quote:

Originally Posted by leathermang

Were we talking about checking to see if your pulley marks were accurate with respect to crank TDC ?

no,
I wondered if my 2mm results were on the wrong side of the scale, to the right of ot as viewed from the front of the car. My results between the methods seem wildly apart. I was assuming that since the engine rotates clockwise, to the right as viewed from the front was btdc.

leathermang · #13 11-23-2011, 06:35 PM

Brian, Thanks, but no way you learned that from me....
my brain this evening got caught up on ' ot '..... what does that stand for ? Maybe I am having a senior moment ?

leathermang · #14 11-23-2011, 06:38 PM

I think we can conclude you need to clean the area around the front of your engine... really clean on that area with markings... then take some white paint with your finger and mash it into the markings... wipe off the top surface to leave it in the markings.... it should have BTDC and ATDC marked there... (?)

fochs · #15 11-23-2011, 06:38 PM

Quote:

Originally Posted by leathermang

Eric, are you just checking for fun or is their a performance problem you are experiencing ?

This is not for fun. I want to establish my chain elongation value. When I tried to time my ip using the bubble method, 24 degrees to the right of ot as viewed looking down from the front of the car was seriously out of whack. black smoke no power etc. I know it is not as accurate as we had discussed on a different thread, but it was repeatable several times. I have tried the drip tube method, and got no fuel at the attempt and do not know why.