HOW did you check, the process is important.
So I measured the P-V clearance every 10 degrees from 30 before to 30 after TDC and then I subtracted the valve lifts derived from the graph.
I wanted to do this, but the top of my retainers are curved, making accurate and repeatable measurements next to impossible.
Thanks Rick. What I should have said, to make it a little clearer, is that because I had to remove the rockers,
the actual valve lifts became removed from the measurements. Since I could not measure the real P-V clearance -
I had to do a little math. Using light pressure checking springs, I measured the distance by pushing down on the
valve stem until it contacted the piston every 10 degrees from 30 before to 30 after TDC and then I subtracted
the valve lifts derived from the graph.
If you look at that graph closely, that camshaft is single pattern with a 108 degree lobe separation, is ground straight up,
has .450" valve lift, a ~270 degree seat-to-seat duration, a ~210 degree .050" duration, and about 50 degrees of overlap.
That is incredibly close to the ISKY 264 Mega camshaft that I'm using - the numbers from my cam card are: 264 degree
ADV duration (ISKY uses .007" and .010" instead of .004 (graph) for seat-to-seat opening and closing), 108 degree lobe
separation, is ground straight up, has .450" valve lift, a 214 degree .050" duration, and 48 degrees of overlap.
The only difference is that I will be using all 1.6 ratio rockers to get .480" valve lift.
It's certainly close enough because all I'm trying to do here is make sure I have enough clearance that the valves don't crash
into the pistons during the valve overlap period. I knew I was safe because the previous Crane camshaft had more lift and
duration than this ISKY, and I measured using the clay method 15 years ago with the Crane cam. Since I did this cam change
with the heads and intake still installed, I could not use the clay method this time. So I had to use the method above.
I would rather actually check than make assumptions.
BTW, I found this on Grumpy's:
the best method would be to use a 1.000" dial indicator and
magnetic stand ....bolt a 1/8 thick small plate to valve cover
bolt hole then stick the indicator in place on the steel plate .
(sometimes a SBC fuel-pump cover works great)
attach a degree wheel and pointer and find true TDC ,
then turn engine over till 10 degrees BEFORE TDC-Overlap
to measure Exhaust clearance . (8 -to- 12 deg closest points)
at 10 deg BTDC ...place the 1.000" dial indicator's point on
the flat part of the spring retainer , zero the indicator,
and with the set-screw backed out of the adjuster nut, take
a wrench and turn the adjuster nut till you force the valve to
bottom out against the piston's exhaust notch ....read how much
the dial indicator traveled ...that's your Exhaust clearance
back-off Exhaust adjuster nut back to ZERO point on dial indicator
now, repeat the same procedure on the Intake side ...but this
time turn engine past TDC-Overlap to 10 degrees AFTER TDC
then check Intake clearance .