@rene4406 posted:And if I believe what George says, open chamber cylinder heads give more valve clearance at low lifts. My maximum lift is 0.62''
Yes, I believe that is correct. The open chambers unshroud the valves sooner, or at lower lift. So you get them to work (flow) sooner.
In that sense, they are better then the closed chamber heads.
You actually need to measure the maximum lift since it varies from the published lifts. Hydraulic lifters don't give 100% lift and solids, you need to deduct the valve lash clearances from the advertised lift.
The efficiency of the hydraulic lifter can vary from manufacturer to manufacturer although they will tell you it doesn't.
The old "anti-pump up" hydraulic lifters were the most efficient. I had a set of those that sounded like solid lifters. They were loud.
Also the oil pressure varies the lift with hydraulic lifters as well.
.620" is nice but it probably will measure out at something like .605 or .610? It is right in the zone where you want it.