Andy
I used to use Knights engineers in Norwich, I can remember John Knights saying leave it with me and will try and find something and he did, I believe he was looking through old Hepolite books, maybe one of those old books would be a start.
I used to use JP pistons Australia with some still in use today without issues and were very reasonable in price, I then had the odd problems with wrong pistons but same part number and loose pins. So I then went west to Arias pistons that were high quality
forged alloy and with some old engines being long stroked and small bores so little oil got to where needed, could specify the old type of non aggressive cast rings and pin fit, even making only 6 pistons of 4”inch bore came out little over £120 each when the cast JP small Triumph motorcycle were £80 so got some surprises. Photo of what know it all people do, the deep section compression rings intended for diesel engines with egressive oil control made the engine so tight they added 12volts to the huge 6 volt starter that then climbed up on the ring teeth to tear the bearer out of the alloy crankcase. The replacements I had made with fraction of the cast iron weight reduces so much of the stresses.
