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Marv:
     Just some thoughts on alternative engines for airplanes.  In a single
engine application one can't have an overly reliable a powerplant.
You've spent all that time building your airplane and any sort of in-flight
power loss puts the whole investment at risk not to mention your own
sweet self and whoever is with you.  Automotive engine adaptations
are a poor risk for airplanes, they have to operate at rpms higher than
they were designed for to develop the requisite power.  Piston travel
per mile traveled is a lot higher and that means wear is higher and TBOs
will occur sooner.  PSRUs are short coupled and propeller loads on
bearings are not as well distributed as they are in the aero engines.
Lycomings and Continentals are designed to operate behind props, they
deliver their power at rpms consistent with propeller tip speeds and in
spite of the age of their design and their higher cost they are highly
reliable when operated properly.  Yep, it is an Experimental airplane and
you can do what ever you want, but I maintain that the engine is one
thing on which one ought not to compromise.  The new diesels which
may soon be available are at least designed to drive propellers.  There
have been a good many articles written on why automobile engines are
not well suited for airplanes so anyone hoping to save a few bucks
ought to think twice and really read up on the subject.  I have little doubt
that some day such automotive adaptations could prove worthwhile.
For now, go for reliability.  When the fan stops in a single engined
airplane you are going down and it won't always be to a runway.
Better bone up on your flame out approaches.  That's two cents from an
old and not too bold test pilot.

Cheers,
Pete