Lou wrote:
I'll agree with the automotive engine with PSRU being heavier, but are
you sure about your other statement "the lighter the better"?
I'm currently looking at an engine that is 100lbs lighter than the one
recommended for my plane. Although cutting 100lbs from the total
weight is a dream come true, it brings up the question of weight and
balance. I can move the engine forward to make up the difference in
balance, but I don't know how far or how to find out.
Lou

You weigh the airplane without the engine installed and
calculate a balance point for it. Knowing the weight of the engine, you
then figure the arm at which it needs to be located to bring the
airplane's empty CG to the point the designer calls for it. Not a big
deal at all. Pages 134 and 135 of William Kerschner's Advanced Pilot's
Flight Manual shows how.

Dan