I'd like to get a setup going where I can analyze cam geometry and valvetrain response out-of-vehicle. Will probably come in handy for any valvetrain upgrades/troubleshooting/experiments that come along.
I only have stock cams on hand, so first up is the 2.5 turbo stock roller cam.
The center hub of an adjustable cam sprocket is bolted to the cam.
That hub then gets centered on the precision rotary table.
A stop arm is bolted to the head and clamped in a vise.
The rotary table is bolted to the table.
At this time the cam can be turned with 30 arc second precision arbitrarily. Measurements can be made on the valves, lobes, or anything else, with ease.
The hydraulic lifter was made solid using shims, so zero valve lash. (described in another thread)
The setup was highly repeatable. I could turn the cam 360 degrees and come back to the same 0.050" lift spot and the rotary table dial read within 10 arc seconds of the previous full rotation. Also, I verified the setup is not twisting excessively by indicating off the head gasket surface during the highest torque part of the rotation and verifying there was no significant movement.
Looks like the exhaust valve on the stock 2.5 turbo roller cam specs are:
Duration from 0.050" open to peak valve lift = 50 degrees
Peak valve lift = 0.414"
Duration from peak valve lift to 0.050" from closed = 51 degrees
The peak valve lift was easily discernable within a fraction of a degree on the rotary table, using a 0.001" indicator.
So total duration at 0.050" valve lift is 101 degrees, and peakvalve lift is 0.414". I'd say the error in degrees is +/- 1 degree, and for the peak lift, the error is +/- 0.005".
Does this sound right? The FSM has very different numbers but doesn't seem to specify the lift its measured at.