Hi,Yes very simple operation. Remove both cam covers, then while watching number 1 cylinder cam,rotate the engine until the lines ,as in Paul's picture line up with the notch in the washer. Check the other side(left ) is close ,then look at the crank shaft damper. the timing mark should close as possible to Zero -0- but often it will nearer to 5. if it is past 5 and nearer to 10 ,then the chain is worn and needs replacing.
A tip I learnt a while ago is to replace the chain then using the offset keys, Advance the cams 2 degrees to give more low end power .
To learn the basics of Cam 'degreeing' you need to know a few steps first.
[i] How to check that the marks on the timing damper are correct (mercedes are almost always correct)
[ii] how to set up up the dial test indicator
[iii] understand what the cam is doing when the dial test indicator begins to open the valve and why that is so important to get an engine running as it was designed.
On our M-100 engines we check on the actual lobe.
This involves checking on the clearance ramps of the cam lobe. The clearance ramps are the slow lifting portions of the lobe which provide a smooth, transition between the base circle and the cam flank on both the opening and closing sides of the lobe.
On the clearance ramps, the first .010" or .015" of rocker arm movement is usually at the slow rate of .0005' per cam degree. In addition to gradually taking up the valve lash (necessary because of valve expansion and small deflections of the valve gear components), the clearance ramp provides the initial, gentle acceleration of the valve off its seat.
Only the end of the clearance ramp directly adjacent to the cam flank is actually used to open and seat the valve, while the remainder is used to take up the clearance and compensate for small deflections or runout in the valve gear. Since the clearance ramp rate of lift (velocity) is .0005" per cam degree, a slight error on your part of say .001" in checking the valve seat timing at a certain point on these clearance ramps, could account for 2 cam degrees (4 crank degrees) of error in determining the timing point . And it is very easy to accumulate .001" error if the dial indicator's stem is not running parallel to the lifter (cosine error) or if you view the dial indicator's calibrations from an angle (parallax error) or if the cam bearings are worn slightly.
This why it can pay to remove the rocker arms to remove influences on the cam movement.
Obviously then to properly determine the position of your camshaft in the engine, the cam timing must be checked at a Rocker arm height off the base circle where the velocity (rate of cam rise) is high enough so that small checking height errors of .001" or so will not result in gross timing damper reading error.
Many years ago a standard height was sought after by ISKENDERIAN racing cam engineers where all racing camshafts could be timed to give accurate results and in 1958 it was decided and later published in their top tuner's manual, "Valve Timing for Maximum Output" that .050" lifter rise off the base circle would be the accepted standard for their camshafts. This figure was ideal because it was Not far enough off the base circle to confuse the engine builder when timing the camshaft, and it was high enough to show effective valve timing (a point where the valve is far enough open to pass an effective air flow). Also, the velocity (rate of cam lift) of most camshafts is approximately .004" per cam degree at .050 ' lifter rise. Therefore, a .002" error in checking height would only affect the Crank Damper reading about 1 crank degree as shown in this picture. The ISKENDERIAN .050" lifter rise check was actually how Daimler engineers specified the correct method of checking cam timng ,who came first,the chicken or the egg ?
to begin your check of the camshafts, rotate the crankshaft until the No. 1 cylinder intake rocker arm is on the base circle (heel) of the cam lobe.
Position the dial indicator stem parallel to the lifter in both planes, and preload the indicator's stem .050" - .100" on the Lobe.
Rotate the crankshaft clockwise several times to determine the runout or eccentricity of the base circle. This should not exceed. 001 and should be centered equally on both sides of the zero on the dial indicator.
(you doing this to see if the lobe is worn and the cam is turning straight in the head)
Rotate the crankshaft clockwise until .050" dial indicator movement is detected and read the mark opposite the stationary pointer. It should read intake opening before T.D.C. (depends on which cam s your m100 has,the timing specs are different between the different market engines) .
Record your reading and continue rotating the crankshaft watching the lifter reach full lift and begin to descend and stop the crankshaft's movement at .050" dial indicator reading before zero.
The reading opposite the stationary pointer should be intake closing at after Bottom dead Center.
Record your reading and repeat your check of the opening and closing points of the intake cam to insure against human error in reading the indicator or crank damper .
If the cam is opening or closing at a different position compared with the factory specs and your chain is NEW, then you can fit keys which will move the position of the Cam wheel on the cam shaft to make the cam open and close Early or late.
As I pointed out before,you can alter the opening to make more power down low (normal driving) by advancing the cam (opening earlier) or more power at the top by retarding the cam (high speed driving) .
quote:
12-14-2004, 11:49 PM #8
Tom Hanson
MBCA Member
What the heck, try to stuff a MB 6.9 liter V8 in it. What a machine that would be..
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Tom Hanson
Orange County Section