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TX007
11/13/18 10:21am

Why does a camshaft make the engine “lope” at idle?

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    Blockheads
    11/13/18 10:51am

    This is typically only in high-power (race) motors. They are typically designed for high-RPMs, and thus have more valve-overlap. Valve-overlap is typically fine or good at high-RPMs, but is horrible at idle. This doesn’t matter for racecars, since their idling performance is real low on the priority list.

    Imagine making each lobe “fatter”.  Doing that will increase the overlap.  It’s necessary on high-RPM applications because of reasons that I don’t want to go into now...

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    JTSnooks
    11/13/18 11:13am

    To expand on that a bit, the overlap means that both valves are open at the same time during the intake stroke.  At low rpm this means you get a poor mixture in the cylinder and your compression and fueling are really inconsistent and hard to control, which results in the engine running unevenly.

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