Quote:
The old Chevy Power engine book recommends having the rocker arm perpendicular to the valve at 2/3 lift. That is lower than the 50% or mid-lift recommendation that is most common.
Heres my two cents. The problem with the attached picture is the rocker arm is perpendicular to the valve at full lift. Not mid, not 2/3, but full lift. This is a .557 lift cam, 1.95 installed height on the springs and CAT Rockers. Although this results in greatest NET lift, it does affect valvetrain stability and other performance aspects. For argument sake, let say the only direction we can move the shaft is up or down. If we go down, the rocker will never be perpendicular to the valve stem in this application. Raising the roller tip by use of lash caps would also make our situation worse. Our only other hope to acheive the mid lift or 2/3 concept is to raise the shaft in relation to the valve.
I'm not saying there isn't an application that may require the shaft to be lowered or valve lash caps to be installed, I'm just saying that spacing the shafts up for proper geometry is necessary in some applications such as this.
All I can add is this, if anyone is having valvetrain issues or is curious about proper geometry, talk to Mike @ B3 Racing Engines. You won't find a nicer guy that is willing to go out of his way to help resolve your issues.
While my problems weren't relative to clearance, the geometry was incorrect. Shifting any higher than 5600 would result in loss of perfromance. After correcting my geometry, I can shift the car at 6500 with no loss of performance. I can"t thank Mike enough. Give him a call before you buy other parts or grind on your stuff. I think you'll be glad you did. 
| 
