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Old 02-24-2003, 10:30 AM
Fimum Fit
Posts: n/a

With a chain driven over head cam motor, if you turn it over backward, you will put a lot of stress on the tensioner side of things (which wasn't designed to deal with such stresses) because the chain will be pulling the cam through the side which ordinarily just floats along, and in a few cases enough slack may develop on the side which normally pulls, to cause things to jump a cog -- this is even more likely on belt-driven overhead cam motors. In a few rare cases, the cam profile on the closing side of the lobe may also be so radical as to cause galling or jamming if it has to lift the valve open. On the other hand, if you have a gear driven cam on a pushrod engine, like an old Volvo or some of the German Ford V6s (also used in Rangers and Aerostars) you can turn them any way you please with no problems, and the same is _usually_ true of mildly tuned pushrod American V8s and V6s which have very short chains to the cam in the valley between the cylinder banks.
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