Jerry,
I bought a Lycoming IO-360M1A/B with horizontal induction and set
myself for some unexpected work and expense. However, this wasn't becaause
the induction was horizontal, but because the sump is wider and the inlet
pipes are too close to allow the exhaust pipes to fit in between them. The
standard Snowline exhaust recommended by Lancair fouled up against the wider
sump so I had to get a custom exhaust made at $$$$. We weren't able to
get this to fit between the inlet pipes, so it passes around them, widening
the frontal area. This meant that the lower cowl didn't fit, and I had to
cut out some material and make chipmunk cheeks to clear the exhaust. We
weren't able to rig a crossover exhaust inside the cowl, so I have two
parallel two into one pipes. Whether the supposed extra efficiency of
horizontal induction more than offsets the power loss for not having a
crossover will become clear when I fly.
If you're going with fuel injection, make sure you get the bracket that
offsets the fuel injection (four legged) spider from the center of the
engine to give you clearance for the upper cowl.
If you want a forward mounted governer, you'll need to put a little
power bulge on the upper cowl (and be prepared for a lot of tinbashing to
make the baffling fit over the front of the engine. Not a big issue.
Make sure you get the shorter of the two dipstick options so you can
close the oil filler door in the upper cowl.
Bottom line is it's possible, but the wide sump makes life awkward.
However, presumably the large oil capacity offers better cooling etc.
Whether this is what Superior were alluding to, I don't know.
Let me know if you need more details.
Regards, Chris.