Ok, so I've replaced the chain in my 617.910. It is now perhaps half a degree better than it was before the chain replacement, but the crank scale is still reading 15+ degrees ATDC when the cam notch is lined up with the mark! (pics attached)
Given the measurement margin of error, the 15 degree offset seems suspiciously close to the 18 degree offset produced when the chain is off by one tooth at the cam. I'm wondering if it skipped a tooth at some point in the past, perhaps when the chain was replaced previously (it was an IWIS chain and had almost no wear). I know this "skip" didn't happen during my recent chain replacement, because at no point was either end of the chain not under tension or out of contact with the cam gear. I didn't even remove the tensioner. In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... Apart from the scale, is there any other externally visible reference mark on the crankshaft? I want to rule out that the harmonic balancer/scale has come loose or wandered, something that seems to happen occasionally, eg if someone impatiently reinstalled it during front seal replacement. If possible, I'd rather not have to remove a prechamber to check piston position, so I'm hoping maybe there's some kind of reference mark on the crankshaft that can be checked against the scale. And given how hard it sounds like it is to properly install the balancer once removed, I'd rather not touch that either if I can avoid it. Would removing the lower oil pan be an option as a means of seeing the movement of #1 conn rod towards TDC? I haven't checked if the pan can be removed in-situ, but intuitively it seems like perhaps it could... D. -------------- next part -------------- A non-text attachment was scrubbed... Name: %IMG_1711.JPG Type: application/applefile Size: 53662 bytes Desc: not available URL: <http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.bin> -------------- next part -------------- A non-text attachment was scrubbed... Name: IMG_1711.JPG Type: application/octet-stream Size: 910453 bytes Desc: not available URL: <http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.obj> -------------- next part -------------- A non-text attachment was scrubbed... Name: IMG_1727.jpg Type: image/jpeg Size: 1361447 bytes Desc: not available URL: <http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.jpg> _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
