Ken if you are willing to make the cowl slab sided up to the rubber
bushings on the motor/psru  plate you will have about five inches of
clearance between the engine block and the upper motor mount
tube for exhaust pipe bends and water pump plumbing. You may 
then worm the 32 inch long exhaust pipes down and around the landing 
gear tubes and out the bottom if you wish. You will have
to shorten the rad slightly but a slightly wider rad is now
possible.

You still have the problem of the extra drag of the external 
muffler on the bottom of the airplane. Note the rubber bushings 
are moved outboard from the previous drawing. The mount is laterally
located by the green tubes running back to the RV4 landing gear 
sockets. Moving the rubber bushings outboard always solves
a lot of clearance problems around the left side of the engine.
On the RV4 it also leads to a much simpler mount with lower 
stresses in the tubes.

Paul Lamar
 
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