rmbuilder

Harrisonmirage,
Part of the confusion is in the calculations. Overlap is a direct function of duration and lobe separation. The zz502 cam has a LSA of 110* and that is ground into the cam and cannot be altered without regrinding the cam. You cannot open or close your lobe separation. The lobe separation angle is the fixed amount of degrees between the intake and exhaust lobe. If a cam is ground with a 110* LSA and the intake centerline (ICL) is set at 110* ATDC and the exhaust centerline (ECL) is 110* BTDC, the cam is straight up. If you advance the ICL closer to TDC by 4* the ICL becomes 106* ATDC, the ECL moves away from TDC a corresponding 4* and becomes 114* BTDC. No matter how far you alter your installed ICL, the lobe separation and duration remains the same, as does the overlap for this cam. Given 224*/234* @ .050” on a 110* LSA, the overlap for the zz502 cam will always be 9* @ .050”. When you advance or retard your cam all you are basically doing is moving your overlap crossover point in relation to TDC.
We always use seat-to-seat figures (adv duration) to calculate overlap because it will give a more accurate representation of the entire lobe.
The differences between adv duration and .050” figures give the indication of lobe intensity, which may alter overlap by inch/degree calculations but not by degrees of rotation.
Bob

HARRISONMIRAGE

When I say I retarded my intake lobe I meant I had it reground,thus changing the lsa to112.

HARRISONMIRAGE

Back to my original question would a cam with more seat to seat overlap have more reversion.Most people seem to be interested in .050 figures only but I would think seat to seat must have an effect.I would also think a motor with weak intake vacuum at idle would have less reversion as well.I like to here everones opinion.I don't count sheep at night anymore I visualise cam lobes.