MP .474 purple cam

I agree with Coyote Jack. The total duration does remain the same but with the higher rocker ratio lifting the valve faster the duration at .050 is increased somewhat. I don't think it makes a tremendous difference, probably only 1-2 degrees but it does change. I was recently speaking with Jim at Racer Brown cams and he confirmed this.

I think what Brambles was referring too as far as the mopar duration not being accurate is because the bad angle the lifter is in comparison to the rocker arm. This causes a little lift and duration to be lost. I've heard lift loss is close to .020" but haven't measured it to confirm it but the next time I rebuild an engine I plan on checking it. If everything was aligned up straight (lifter to pushrod to rocker arm) there wouldn't be any loss.