Port timing calculator help needed

[phil23fair]

I'm trying to use the Lambretta Images Archive port timing calculator and I hope there's someone out there who can give me some clarification on a couple of the measurements:
First "Piston Crown to Top of Barrel at TDC": Is this the very top of the piston crown or the edge of the crown to side of piston?
Second "Piston height inlet side": Is this just the length of the side of the piston or does it include the crown?
And to confuse the issue even more could these measurements be to to edge of the top ring? I'm sure there used to be a calculator that all you entered was the deck height be that positive or negative and it sorted it all out for you but I have looked all over for it and cannot find it.

[Warkton Tornado No.1]

TBH I am not familiar with that particular port timing calculator, but any timing is assumed to be controlled by the very edges of the piston. Rings are in place to create the seal to enable running & the top edge of the top ring would only control timing if it were level, or above the crown edge, as in certain Dykes rings pistons, (fortunately not very popular nowadays. Though if anybody is keen to buy my Ancillotti Dinamin '175' piston that is 66 mm oversize, get in touch )

The top edge of the piston will control transfer & exhaust, regardless of whether the crown is domed, flat or even dished. Any crown radius will not affect anything other than in it's proximity with the head (squish)

The bottom edge of the piston will control inlet duration, though the opposite side needs to maintain 'closure' of the exhaust port.

Any piston ports (windows) will be part of the transfer process or inlet in the case of reed valve engines.

I hope that helps