-> Here's how it would work. (I'm not Marcus so I won't even attempt a
->cool ASCII drawing.) On the tense side of the chain, (driver's side),
->install a very small idler sprocket in the middle of the chain's travel
->between the crank and cam sprockets. This sprocket would 'push' into the
->chain from the outside, effectively advancing the relationship of the cam
->sprocket to the crank sprocket. Adjustment would be provided by an Allen
->stud, threading into the side of the timing chain cover. The Allen stud
->would be held fast by an outside nut.
-> The slack taken up by the adjuster would be compensated for by the tension
->spring on the 'loose' side of the chain, as currently exists.
-> 'Zero' could be achieved at the center of the adjuster's travel by
->using an offset key, or Zero could be set wherever convenient for the
->particular engine.
The problem is:
Take a quick compute of the side load onto your sprocket. On a 6
cylinder engine, the torque required to turn the cam, move all the
lifter gear, compress springs, etc is non-trivial. I don't know much
about 4 cyl cars, but I figure the order of magnitude would be the
same. Such a sprocket would need to be rather heavy duty, have a real
pivot point, and I think a small allen wouldn't really be up to it.
Such a system is used in a few vehicles I can think of, some on a more
active basis than you plan. Hooking a servo motor up to the equivalant
of your allen screw and a computer gives variable cam timing dependant
on other input factors...Ask the folks @ Toyota about it, or Honda,
though they do it at the cam itself.
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