Starting in 1983, when I discussed Duo-Art cross valves in a technical
session at the AMICA Chicago Convention, this topic has been hashed and
rehashed to the point that no one really cares about all the details.

The simple facts are
(1) cross valves _may_ leak and cause huge problems;
(2) cross valves that do not leak have marvelous performance;
(3) replacing the cross valve seats with round valve seats
_may_ be a disaster.

In (3) above, replacing the cross valve seat with a round valve seat
upsets the geometry balance of the valve system because it changes the
area of the opening by 30%.  To compensate, and restore the balance,
the valve body must also be changed.

Good, fresh leather like the original will render a cross valve of
superb performance if all surfaces are true and air tight.

This is all the collector/rebuilder needs to know.  If anyone really
wants to change the valve seats, they can contact me for the details.

Bob Taylor