Re: Dual thrust cam bearings.

Dear Bill (and the Group),

I've not found any advantage to a full-circle thrust-flange on the #3 cam
bearing unless the engine spends a significant amount of time above 5000 rpm OR
the cam is being asked to transmit an unusual amount of power to the valve
train (dual springs, high-lift, etc.)

If you want to form a tang on the cam bearing shell I suggest you carefully
mark the BACK of the bearing shell then use a Swiss file (or similar) to cut a
'ramp' of suitable size in the STEEL shell.  Then make up a swaging punch of
suitable size (ie, NARROWER than the tang by the twice the thickness of pewter
bearing material on the inside of the steel shell) and use a junked case as
your die.

I've only seen a couple of engines where the #3 cam bearing has spun and they
were always in conjunction with a catastrophic lubrication failure,
after-market cam gear and so forth.

Keep in mind that the cam spins at half the speed of the crank, and that when
the cam is properly fitted to its bearings, it will have quite a bit of
clearance at normal operating temperature (assuming it is ground on a cast iron
blank).  

-Bob Hoover