On Apr 16, 2:50*pm, "Morgans" wrote:

How long it will last is another story. *If you set it to not boost too
high, it might last a thousand hours.

I doubt it. They're an 1800-hour engine that almost always need top
overhauls well before then, sometimes before mid-time. Boosting it
would overstress already-weak valves and it wouldn't go too far at
all. And with the traditionally low oil pressure these things have,
the bottom ends wouldn't last too long either. The crank was not
nitrided and wears rather rapidly anyway.
The same basic engine was boosted to 75 hp (A-75) using a
higher redline and heavier piston pins and a slightly larger carb
venturi and main jet. They got 80 hp (A-80) by raising the compression
to 7.55:1 from 6.5 as well as the higher redline and bigger carb. And
that's about as much as they dared get from 140 cubic inches with the
engine being as light as it is.

Dan