As John Clark indicated yesterday it is difficult to know
"Advertised"duration based on @ .050 lift. Many manufactures will state
"Advertised" duration and yet even that is at an ambiguous .004 or maybe
.006 lift and not necessarily zero lift as many would assume. My
understanding is that lift @ .050 was chosen as a standard because many
thought that there was no meaningful flow below that point. Hence,
"effective" duration would be more measurable cam to cam at lift @ .050.
Having said that, I have a 204 duration @ .050 came for my daily driver
Mopar. When compared to similar cams it seems to be in the advertised high
250's to low 260's duration, yet the manufacture states it is an
"advertised" 280 duration cam (measured at .006 lift). Overlap specs. on the
cam would follow that rating. Basically I was told that it seems the
manufacture was looking to get similar characteristics of a mild cam, but
the cylinder scavanging benifits of the long overlap (all be it at very low
lift).
I realize that the lister was basically trying to convert on older cam to
more modern specs., but I think it will take a dial indicator and a degree
wheel to really know the correct answer.
Tom Witt
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