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cam confusion

This is a discussion on cam confusion within the Internal Engine forums, part of the LSx Technical Help Section category; i dont understand the cam numbers what do they mean...

  1. #1
    Junior Member
    Join Date
    Apr 2008
    Broken Arrow

    95 f-150

    cam confusion

    i dont understand the cam numbers what do they mean

  2. #2
    Track Whore 570SX's Avatar
    Join Date
    Jul 2008
    Central Florida
    1989 Nissan 570SX

    you'll find more info if you go to a major cam manufacturer's website, i.e. Comp Cams or something.

    basically there's:
    advertised duration, measured in degrees: theoretically how long the valve is seeing a force exerted on it by the cam. not particularly relevant to anything, but you can still compare cams against each other based on this number. degrees are of crankshaft rotation.
    maximum lift, measured in inches at the valve (or mm if you're looking at imports): the most the valve opens at any point
    duration @ 0.05" lift: how long the valve is at open at least 0.05". much more indicative of actual duration. interestingly, the closer this number is to the advertised duration, the quicker the cam is ramping up to max lift, which is a good indication of how harsh the cam will be on the valvetrain components.

    for any of these things, larger numbers generally mean more power in the top end, with sacrifice of low end. read up on a cam manufacturers' websites for more in-depth coverage.

    there's also lobe separation, measured in crankshaft degrees as well. for this, the lower the number, the more lopey the sound, and it will drastically affect the difference between top end and low end/midrange power. a few degrees less separation can make a cam come alive at 5000rpm instead of 3000rpm.

    check this out for some reading:
    scroll to the bottom and start reading.
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  3. #3
    Member chieftransam's Avatar
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    Nov 2006

    2001 Pontiac Trans Am M6

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