How can the cam move back and forth when the angle on the timing gears pushes it back against the thrust plate when the engine is running? If the cam and crank had straight cut gears, or a sloppy chain drive, "cam walk" could be a problem. That's why we put a "thrust button" on the small block Chevy race engines when we ran a double roller timing chain, and reinforced the timing cover by brazing a heavy flat washer in the middle of it. Cam walk on a stovebolt six is impossible.
Jerry
