Valvetrain Geometry

RustyRatRod said

So, you think that 3 degree difference from 45 makes an appreciable difference? Comparing those 3 degrees to the 14 degree difference from 59 to 45, I can't see it. Especially if they run as well as they do with the 59 degree lifter bores. Evidently, it just doesn't matter "that much". I've sure seen that angle subtract a bit from the gross valve lift, though.

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I’m not sure I understand the reference to 45 degrees. 48 degrees is perfection for the SBM lifter angle. Factory stuff was 59. That’s the comparison I see.

As far as the loss of lift - that can be recovered by designing the rocker arm properly. Move the adjuster toward the rocker shaft and the rocker ratio increases.

What the bad geometry does do is create side loading on lifters, rockers, shafts and pushrods and creates a pushrod motion that ‘see-saws’ instead of traveling back and forth in a nearly straight line. All this wasted motion creates increased friction losses, increased harmonics and other unbalance forces and makes a slightly stronger valve spring necessary. It’s just increased inefficiency.