Shaped pistons?

[Ken Crawford]

Has any manufacturer ever made piston valves that were not round? As in slightly oval, or any other shape? Successful execution of such a valve section would eliminate valve guides and lead to quieter and more reliable action while achieving more precise alignment.

Dumb idea? Been done before?

[Kirley]

Massively more difficult manufacturing and repairing.
You can't just spin a thing and make an oval.
Instead, you need to spin a thing that's spinning a thing (think Spirograph).

Oval(ish) ports, on the other hand, have been used quite a bit. Like the Conn 2XJ/K horns.
And the trumpets that the Saturn Water Key guy makes:
http://www.deniswedgwood.com/ovoids.html" target="_blank

I know, not what you were suggesting.

[Donn]

or any other shape?

Square wouldn't be awfully hard to make. Round has the least surface area, though, of any possible cross section. Probably the strongest shape for the enclosing cylinder, too.

[Sousaswag]

The Holton short action pistons almost look like a really long rotor to me. The ports seem very square-ish.

[imperialbari]

Weren’t some of the first valves from the 19th century square?

Klaus

[windshieldbug]

Too much surface area to keep lubricated!

[Three Valves]

Too much surface area to keep lubricated!