Piston to valve clearance

[Ed Wright]

I only do "valve drop" measurements to verify all cylinders have the same valve seat-to-valve pocket travel. I would never just do math to check my valve-to-piston clearance. I actually measure it in 2 degree increments 20 degrees from TDC. I have found the closest point being ten degrees from TDC to almost never does apply to my stuff. I measure it with the springs I'm going to run. I have an old Mr. Gasket on-car valve spring checker that I have modified to fit my Jessel rockers, to pull them down against the pistons. I use a long 1/2" drive break over instead of the torque wrench it was meant to use for checking valve springs. Checking with weak checking springs always show less room than it will have running.
I measure it with the cam two degrees further advanced than I expect to run it, and backed up two degrees further than I would expect to run it, on a new engine. After I settle in on where I'm going to be running the cam, the next time it's apart, if I have room, I close it up to the minimum. My pistons have a clean ring like the face of my Manley valves, and a round dark spot for the dimple in the center.

I quit using modeling clay about 1970, when Carrol Caudle told me "Ed, give that crap to a kid to play with, that is what it is meant for." LOL

If somebody tells me they bought an engine, and how much clearance should it have, I'm going to tell them way safe to keep them out of trouble.