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Old 10-29-2012, 08:40 AM
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Originally Posted by wwilliams181 View Post
I honestly think you will be fine with this cam. The problem most are talking about is that the Rpm range is narrowed and the loss of cylinder pressure due to the added overlap.
While it's 100% correct that overlap alone doesn't cause a loss of cylinder pressure, a large amount of overlap implies that there will be more duration, all else being equal. An increase in duration in turn implies there will be a later-than-normal intake closing (IC) point. A late IC point will cause a loss of cylinder pressure, reflected by a lower dynamic compression ratio. So in a round about way, many times excessive overlap could be said to contribute to a loss of cylinder pressure- just not the way that some think it happens.

Overlap can also cause reversion at low rpm along w/a loss of vacuum. This contributes greatly to the 'lope' of a performance cam- which is really nothing more than the engine running like crap at low rpm.

As it is, cam companies have been stretching the envelope for a long time. It's only because of advances including CAD/CAM and in metallurgy that we can get away w/cams as intense as the Comp XE series.

Personally I'd like it if a cam could be ground w/o any lope and retain 20 in/Hg vacuum while retaining all the lift, duration and overlap needed for high rpm efficiency. But because of the limits on materials, valve spring pressure, lobe intensity, etc. this can't happen. Not talking about variable lift/duration/timing valvetrains here- I want a magical cam w/square lobes w/o needing any bells and whistles!
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