[Walt Fricke]

Mark

I think you are worrying about things not worth worrying about in your case. If this was a running motor, and you are just going to plug it into your car, you don't need to check piston to valve clearances. If the leakdowns are good, they are pretty clearly enough so that valves aren't hitting pistons.

If it never ran, different story.

However, the time when valves get closest to pistons is in the neighborhood of TDC overlap (i.e., when things change from letting the exhaust out to letting the intake charge air in). When you get around to disassembling this motor, and then making machining changes to things which will affect clearances, then you do mock-ups and check these clearances. This is the only time during the crank's 720 degree travel that valves get anywhere near the pistons.

The procedure is simple whenever you do it, though - pick a minimum clearance, use the adjusters to push valves down that amount, and carefully rotate the motor, being especially gentle at you are coming up on TDC overlap, and leaving it.

I just laid out $200 for a Harbor Freight borescope. Its scope will fit in a 12mm spark plug hole. The $100 one lacks the capture and transfer to computer etc feature, but might work as well for inspection? A guy could use this with its 90 degree mirror) to watch the valve clearance. Once you saw where exactly it got closest to the piston you could then screw the adjuster down more to see just what your motor's minimum is, which might give you some idea of how much you could bump up the CR (assuming you have piston to head clearance to spare) without getting into valve trouble with the cam you have. This might be a better way of avoiding inadvertently bending a valve stem than the "screw down until one hits when turning crank" approach.