340 dyno chart thoughts

IQ52 said

I agree with the direction of the math but not the duration. To get the movement at the cam you would have to divide the lash by the rocker arm ratio. So you're not going to decrease the duration 10 degrees but more like 6 degrees. Already made that mistake for myself.

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Yes, you're 100% correct. Somewhere In this thread I hastily put my explanation out there without taking into account or mentioning rocker ratio. Thankyou for correcting this mistake.

About 5 or 6 degrees to move the lifter a factor of valve lash divided by rocker arm ratio does sound about right.

For example a lash of 0.015" and a rocker ratio of 1.5 will require the lifter to move 0.010" before the valve starts to move

Since lash comes into play twice on a lobe's rotation, once at the beginning and once at the end. That would be approx 10-12 crankshaft degrees less duration at the valve compared to at the lobe.