[Tinkerer]

Can a direct comparison be made regarding valve overlap between the tight LSA fast ramp cams and the lazy lobes on a wider LSA?

I am finding that even though the fast ramps in question (XE's et al.) have a tight LSA, there is less valve overlap than the lazy lobes with the longer seat timing. Would not the short overlap cams be smoother at low rpms?

Or is the short overlap offset by the faster valve opening, therefore there is actually more flow during the overlap despite it being short?

I understand the issue with the early intake closing event and the noise created by the fast ramp design. However, I would like clarification regarding the overlap. There is much said in the negative for a tight LSA, but with the fast ramps, the overlap is actually less (by the numbers) than the wide LSA-lazy lobe configuration.

For example:

SPC-7 (which I currently have in my 455)
212/225 @ .050"
Intake closes at 75.5 ABDC
Overlap 60.5
LSA 115.5


XE268
224/230 @ .050"
Intake closes at 60 ABDC
Overlap 54
LSA 110


Thanks,

Bill