[SAJ]

The alternative to knurling is Koetherizing, wherein the piston is squeezed through the gudgeon bores by a bolt and thrust bearings into a more cammed shape on the thrust faces. While under this compression it is shot peened inside, relieving the alloy stresses so it retains part of the squeezed in expansion when released.
There was an article on this forum about a portable koetheriser in a truck by Old Motor a while ago.
I just 4-stone honed an engine to straighten worn bores and bought new Omega solid skirt pistons which I resized on my koetherizer by 0.0095 for the worst bore. The others were around 0.005 inch. That engine now runs nicely with no piston slap.
Obviously not as good as a rebore, but fun to do and should last another 50000 miles at least, going on past history with older repairs by the firm which donated the machine to me.
How many koetherizers are left in the USA I wonder? I think I have the only one of 2 that were sent out to NZ.
The engine was a 2.5 litre Riley, not a Model A. Compression pressures are now all 167 psi. 8.8 to 1 pistons used
SAJ in NZ