The making of a Cleveland piston. 
This Photo series shows a Cleveland piston which has been used as an example for making a Neracar piston.
The process of making this piston mimics that of a home-made tapered Cleveland Piston.

The clearance of the Cleveland piston in the cylinder was initially:

Top                              0,33 mm
Near gudgeon pin       0,18 mm
Bottom                         0,11 mm

During the test run shiny areas developed on the piston/cylinder surface, hence, the clearance was increased to:

Top                              0,38 mm
Near gudgeon pin       0,28 mm
Bottom                         0,18 mm

“Clearance” means cylinder diameter minus piston diameter, so a clearance of 0,38 mm means a circular gap of o, 19 mm.

See drawing below: