Obviously, I am not thinking about this correctly.Say the original dowel hole was 0.30" (hypothetical I did not measure) in the cam gear and the dowel rod on the cam was 0.298" so the cam dowel slid right through the cam gear dowel opening. If you bore the dowel hole on the cam gear all the way through to 0.40" that obviously is bigger than 0.30". Bigger is required as the bushing must go in that hole (bushing is larger than its dowel hole opening thus allowing the cam to be slightly advanced/retarded by changing the placement of the offset) (done through use of different offset bushings. The bushing has a hole for the dowel of the same original diameter (0.30"). Since the dowel hole is the same diameter in the offset bushing as well as the original cam gear the dowel on the camshaft cannot be inserted all the way except if the offset is 0 (because this is the only time the 2 would be aligned). if you offset it say 2 degrees (offset bushing) then the hole in the cam gear (remaining after not boring all the way through) and the offset bushing will be out of line and the camshaft dowel cannot go on all the way....right????

Sorry this is tough to describe.