Valve to piston clearance

Worried for this cam with a typical lift/duration ratio? Probably not. Check it? Yes, you know how all this works: it would be asking for trouble to not do so!

Once assembled, you can use this method:
- Replace the 2 valve spring on one cylinder with very light checking springs from the hardware store, just barely enough to close the valves. My checking springs exert maybe 1/2 lb on the valves; the springs in the lifter will put several lbs on the valve... the lifter spring will win.
- Turn the engine slowly, 5-10 degrees at a time, and, starting around 40 degrees before TDC on overlap and going to about 40 degrees after overlap, stop each 5-10 degrees and push down on both valves, and measure the movement. The movement that you find will be your P-V clearance at each spot.
- The most likely minimum clearance points will be within +/-15 degrees of TDC.

If you have good clearance, then stop there; it will be that much or more when running.

If clearance is inadequate or marginal, then do one more step: Since the spring inside the hydraulic lifter is 'outpushing' the very light checking springs on the valves, then the valve is actually being 'hung' slightly open and the P-V clearance measured above will be less than actual running clearance. So you need to measure that actual extra clearance.

- Rotate the engine to TDC on compression stroke for the test cylinder; this will put the lifters on the base circle.
- Check the height of the retainer to a reference surface.
- Back off the valve rocker shafts to let the valves rise to the seats, then measure the extra height on the retainer, and figure out how much the valve has risen.
- Add that to the P-V clearance you found before to get a better number on actual running clearance when the lifter's piston has actually adjusted to its final running position.

Hope that all makes sense!