Valve Timing: S&S vs Others

[Harley Pilot]

Is S&S the only one with different valve timing on front and rear cylinders?, and what are the advantages of this if any?

[FLDavetrain]

Others do too, Cyclerama, fueling to name few. Why is as good a Q as any.

[kd]

Is S&S the only one with different valve timing on front and rear cylinders?, and what are the advantages of this if any?

No.  The spark timing on a 45 degree twin is uneven (potato potato) and air flow can be problematic as it is influenced by the effect of the opposing cylinder in the short shared intake manifold.  Adjusting cam specs is a good way to manage cylinder fill and therefore drivability issues that can occur when intake port velocities are low and flow rates slower.

[Harley Pilot]

Thanks kd , flDavetrain. As always good knowledge here!

[Ohio HD]

S&S and some HD performance cams utilize dual pattern timing.

As KD said, the design intent is the cause of the odd timing. The perceived results are "probably" more mathematical design than actual result of any gain. 


https://harleytechtalk.com/htt/index.php/topic,111272.0.html