The
above isn't as confusing as it looks, once you know what you're looking
at. There are TWO representations. The PUSHROD's in and out motion, and
second, is the Rocker arm's Roller Tip motion for a specific valve lift.
The Valve Lift is shown in the lower right corner, as "VL"
for both the Big Block Chevy (BBC) and the Small Block Chevy (SBC),
respectively.
The
Green
HORIZONTAL lines represent VALVE LIFT and CAM LIFT. The Valve Lift is
shown on the RIGHT; while the CAM Lift is shown by the numbers on the
left side of the vertical green line. MID-LIFT is shown in the middle
with the
YELLOW horizontal line. Finally, the BLUE ARCS are
the different RADIUS` for the TWO critical dimension, TRUNNION to ROLLER
center-to-center, and TRUNNION to Pushrod Cup center-to-center. There
are actually TWO roller tip rocker arm lengths shown for both the small
block (1.350") and big block (1.620").
The
RED circles on the horizontal lines
show the intersection points from MID-LIFT to a Valve Lift of .800", but
please note that they are only attached to the .400" line (4th line
below the MID-LIFT line). That's because we are only showing 1/2 of the
valve lift, since we are only measuring from MID-LIFT. As you can see,
the 4 digit CAD measurement for the BBC is illustrating only .050" (and
2/10s), while the SBC is a little more, at .060". This is for .800"
valve lift!
To the upper left of
the above illustration, you can see the Pushrod arc (in and out motion)
is calculating .400" tappet lift, although we've left the red circles
out of this part. Please note that this is only .022". That is how much
the pushrod should leave it's path as it follows the tail of the rocker
arm around. Measure yours. If it's not our rocker, you'll probably get
sick.
