Posted for "Marko Bewersdorff" <marko@bewersdorff.com>:

>How about a ball valve - those with zero flow restriction? You could
put one
in line and manually control flow - maybe a remote lever of some sorts -
that would be like a cowl flap basically. hmm, I sound too theoretical -
for
the record, I currently have no cooling problems - the engine is still
sitting near the plane on an oil drum, just need to get started on the
engine mount...

A ball valve could work fine as an in-line control if it is the line to
one of two radiators.  In the main line out of the pump; probably not.
As noted in other postings, the Mazda thermostat closes the internal
recirculation loop when it opens to the external loop.  With the
thermostat removed and the bypass plugged, throttling downstream with a
valve could cause serious hotspots in the engine.

Al