Make adjustable cam gears out of stock ones!

What about drilling out the dowel pin hole in the stock cam sprockets and inserting a eccentric bushing to advance or retard the cams. I used to do this on small and big block chevy V8's with roller timing chain sets to dial in a camshaft that was slightly out of spec.. The eccentric bushings came in a kit that included bushings with various different offsets to allow you to dial in a set amount of advance or retard by simply swapping the bushing. I think the kit was made by Mr. Gasket at the time. Ahh, here you go, "Infinitely Adjustable Timing", Summit Racing catalog item #s CLO-9-3100A and CLO-9-3110A. Cloyes Hex-A- Just timing system. This works on the very same principal as what I described above but uses an eccentric bushing that has a socket head on top of it for an allen wrench. This wouldn't be quite as easy to tinker with as a set of aftermarket adjustable cam sprockets, but would be a whole lot more secure in that there would be no risk of the sprocket adjustment slipping. 8)

This is just a shot in the dark, but I'm thinking that perhaps the stock 5M, 6M cam sprockets are beefier and heavier since the valves on the 5M and 6M are physically larger with heavier duty springs than the lighter weight 7M valvetrain parts. More turning effort may be needed to rotate the 5M, 6M valvetrain than on the 7M and thus the need for stronger sprockets. The weight of the sprockets themselves is going to have less effect on rotational torque required to spin the valvetrain than the load placed on the crankshaft by the heavier valve springs on the 5M and 6M. The heavier sprockets could actually be to an advantage in that the rotational inertia will be greater with heavier sprockets, which in turn can serve as a damper to help reduce pulsations and harmonics that are present in the rotating valvetrain. Less overall stress would be placed on the timing belt, the timing belt drive sprocket on the crank, and the cam sprockets themselves due to the inherent dampening effect of the heavier stock sprockets. Maybe someone could check and see how much rotational force is needed to rotate the valvetrain on the 5M, 6M, and 7M engines? All you need to do is use a torque wrench on one of the cam bolts with the timing belt removed and see how much torque it takes to compress the the valve springs on each engine.


Dave A. (preparing to put on my flamesuit) :burn: