[frnkeore]

What I researched was in the minimum 4" bore size but, I would say that it would be relative to the circumference of a bore and it may be relative to the stoke length, also.

It was also dealing with 1/16 x 3/16 vs 1mm x 2mm rings, and not the common wider compression rings of the flathead.

The key to getting a idea of how much HP they can save, is to measure the TQ required to turn the engine, after they are installed.