Duration figures are tappet lift, not valve opening. Solid must take up lash before the valve opens, hydraulic opens the valve right away. This would explain how a 220 @.050 solid will idle like a 210 @.050 hydraulic.
Do I have that right?
I think that is a fairly close comparison. If both cams, a hyd. and solid cam have 220 @.050 duration, you would check each with zero lash. At the lobe they would appear to be the same with 220 @.050, but once you would add the lash to the solid cam, it will loose some amount of duration, because of the slack you have now introduced into it. The hydraulic cam will still retain its original "as checked" duration readings, since it was checked in the same manner of lash that it runs in. Hope that helps explain a little better....
