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Chain stretch
Quote:
Originally Posted by M-Tech
. . . New thought - (Old thought, new approach.) Checked timing chain. Crank on O deg., cam gear retarded over 40 deg. Enough to drop compression. On rubber band engines with collision heads that would bend valves and/or crack the head. On freewheeling engines it would lower compression significantly, depending on the degree of retardation. Are 603s interference engines?
The question at this point is whether the chain is stretched or jumped a couple of teeth. As I read the valve timing procedure in the MB manual (referenced elsewhere on the forum), basic settings would have to be right first, then measure the drop of the valve (rise of the dial indicator). A 2mm drop at 12 degrees ATDC would be correct - but with a tolerance of 4 degrees. Is that +/- 4 (i.e., 8-16)? Beyond that, the chain is stretched too much. . .
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Here is a photocollage of the timing marks in an OM603 engine with no chain stretch. You can see how the marks line up.
I think the PO put in a new timing chain when the cracked head was replaced before I bought the car. I've no idea how many miles are on the new chain but probably very few.
Jeremy
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