Formula, please - valve timing/piston position

[Dynoroom]

Another thing to consider is "piston rock". Most racing engines use pistons with more piston to wall clearance thus when cold the piston moves or "rocks" oven in the bore requiring more radial valve head clearance. YMMV.

[fordboy628]

There are commercial programs out there that accomplish this, some expensive, some "affordable."  Almost all the useful ones however, require the utilization of an electronic cam profile file, such as "Cam Doctor".  You can accomplish what you need to "the old fashioned way" & accurately with the following:

1)  Degree wheel & pointer, both solidly attached to the mocked up long assembly
2)  .50"/1.00" travel dial indicator and stand solidly attached to cyl. head
3)  VERY LIGHT substitute valve springs for cylinder being checked
4)  A LIGHT TOUCH when rotating engine during overlap period if you suspect valve to piston clash  (As opposed to the "Clash" which never had a light touch,
     musically speaking.)
5)  Opening the valve lash to reduce lift @ overlap can give you somewhere to start calculating flycutting dimensions if the dreaded clash occurs straight off.
6)  Light springs on the valves & the indicator on the valve stem can be used to plot existing valve to piston clearance (from the seated valve to the piston top) from
     about 20/15 degrees BTDC to 15/20 degrees ATDC, WITHOUT ANY CAM LIFT.  DO NOT "ASSUME" BTDC & ATDC WILL BE THE SAME, you might be surprised.
     Then graph this out and you have an idea of what that particular setup will tolerate for NET cam lift.  You probably want to measure every 2 degrees or so.
7)  When building up an "orphan setup" the "engine builder" (as opposed to the "engine assembler") NEEDS TO VERIFY THIS INFO FOR HIMSELF, regardless of what
     any others may advise.  Unless the "builder/assembler has a "bottomless wallet".
8]  I like to see .080" inlet to piston clr. & .100" exhaust for pushrod engines running 9k redlines.  IF VALVE TRAIN MOTION IS VERY WELL CONTROLLED, (or " IF
     you're feelin' lucky, punk".) clearance can be as tight as .050" inlet/.070" exhaust.
9)  I reserve the right to change my opinion, at any time, without notice.

Best regards to all,
MB