The design stack up takes in to account all the vairiables mentioned here - block, cam bearing, journal size variations along with camshaft runout. Blueprints were developed with the min/max sizes and runout.

Testing was then performed using these specs.

Production then built the parts within those specs. At least they tried to.

Mass production, tool life, lack of process control, lazy maintenance play into variations in specs. We have all seen it - blocks differing in deck heights, bore sizes, etc.

Even though developed in the late 50’s, the design is obviously robust enough as we have been using these blocks with conventional bearings with high lift cams and spring pressures probably three times more than designed for.

I have seen it many times - product engineering says “build this” then the plant floor says “we can’t with these specs” then things get loosened up.

Tooling and matching has changed tremendously since then.

Today the engine plant can machine and build an engine that rivals hand built/blueprinted engines from the 60’ and 70’s.
Day after day.