You can call the marks anything you like. If you replace a belt the change in the relative position of those marks will not change by more than +/- 0.5 degrees from where they were the last time the belts were changed. Whether the engine will be timed correctly, again, the caveat is, "if you start with a properly timed engine". People who do not accept that must believe that dimensions of metal parts change and that the manufactures are lying about tolerances on bet length, and tooth pitch. And here is another point the never get discussed much. Please note that in my post #21 I said the max error due to belt tolerance was +/-0.75*. That was in error. The tolerance for belt length is +/- 0.75mm which translates to a little more than +/- 0.5*. If you start with a correctly timed engine and the belt does stretch 2mm, then by the time you are preplacing the belts the time would be off more that 1 degree from where it was set, more than would occur if the tolerances of the old and new belts were at the extreme opposite limits. But belt stretch is irrelevant because all it tells you is where the timing is compared to where it was when that belt was new. Now, if belt stretch is an issue that effects timing adversely, why would you not compensate for it want replacing belts? If belt stretch were to account for a timing change of 1.5*, why not time the engine to be 0.75* advanced so that at the end of the belts life the engine would only be retarded by 0.75* as opposed to starting with time dead on and ending 1.5* retarded? Again, I repeat, the caveat is if the engine was timed correctly the last time the belts were changed. If you are confident that is the case, a belt sway is sufficient since the max change due to a belt swap is within the factory spec for timing. If you aren't confident, then check the timing and adjust if you feel necessary. But please stop trying to convince me that 1" drill makes a 2" hole.