ORIGINAL: w8ye
I always set mine so the center of the overlap interval center line is about 5 degrees before top dead center. This varies slightly on the different models.
The important thing is that the last part of the overlap does go through TDC.
A Magnum with the timing mark straight up and down at top dead center will complete the valve overlap sequence just before TDC. It will start and idle great but will be sick at high rpm compared with a OS or Magnum with the overlap centerline just slightly before top dead center.
Problem is, W/our gear drive valve train, a shift of 1 tooth shifts cam timing 15* on a Saito. W/a 48 tooth can drive gear. I would imagine the Magnum & OS valve drive would also result in excess shifts in valve timing W/a 1 tooth change.
We are pretty much stuck W/OEM valve timing.