[ted]

Because of all the manufacturing tolerances in the various spots of an engine to which the camshaft timing is related, it's a pure neccesity to degree in any camshaft being installed.

These variances include:
1) The location of the crankshaft key way.
2) The location of the crankshaft gear key slot.
3) The location of the camshaft dowel pin.
4) The location of the camshaft gear dowel pin hole.
5) The cam to crankshaft center to center distance.
6) The gear set center to center distance.

If any one of these are off, then the camshaft timing will be altered. If per chance, several are off in the same direction, either positive or negative, then the amount of error will be "stacked up" or increased by the sheer addition of the amounts of error. Hence the need to actually check the camshaft phasing versus just lining up the marks.

For those engines that have been alligned honed, timing sets are available in various shorter amounts to compensate for the reduced center to center distances in the block that resulted.

And here's another one. The next time you're degreeing in your camshaft, check every cylinder, not just number one. You may be in for a shock depending upon the cam manufacturer.