Right, but he measured 57° between flanks. If you assume the base circle is perfect that determines duration, and I do trust his ability to read a protractor. The only other possibility is as he describes runout on the cam and depending where that error in cam profile ends up easily explains what he's observed. Tolerance makes or breaks assemblies, and cams are sensitive to it. Had the camshaft bore and base circle been made in one setup I'd question it as well. There are, however, several setups each introducing error, fact of machining. .008" error when lash is less than that will cause serious problems in cam actuation. In the few production model engine cams I've inspected base circle error has been on the order of .0002".