I have been having some problems with inconsisent timing on my new motor.The distributor is a 57+ style that I purchased as a rebuilt unit last year.When I had the distributor out I did some checking on the existing freeplay of the shaft.The up and down not the sideways as its fine with new bushings.The clearance between the collar and lower body is at .050 and specs are .022-.036.I can fix that with a shim kit I just ordered made by Mr.Gasket.When I checked the upper what I call cam assembly there is another.047 freeplay.When I pulled it off there is no thrust washer-its missing.My question is does anyone know how much freeplay is supposed to be in that cam to shaft?The Ford parts book lists the thrust washer for a 59-61 292  distributor at .020.Seems to be the only one used with the y-block dizzy.That would still leave .027 freeplay.I have a washer on hand correct diameter but its .030 thick..How much freeplay  is really required for cam to shaft clearance?I did some research on the internet and too much vertical freeplay CAN affect the timing.Can also affect wear on the cam gear and the distributor gear because the mesh of the teeth is slightly off.When I reinstalled the original loadomatic just to check my theory,the timing marks stayed as set.Never varied from original set timing even when revved up and returned to idle.The distributor I am working on would return to different settings each time it was revved up and timing marks would "float".I had removed the Accel kit and reinstalled new points so it is not the problem here.I believe its  the excess play in the distributor shaft.