On Thu, 08 Jul 2004 13:22:55 GMT, Richard Lamb
wrote:

Not to labor the obvious, but there IS a little size difference between
4.6 liter and 470 cubic inches...

Richard (no substitute for cubes) Lamb

If we are talking about the same engine, the Buick/Olds aluminum V8,
it's lots worse than that. The original engine was 215 cubic inches
in displacement. That's 3.5 Liters.

By the way, the 3.8L Ford V6 engined Pawnee being used in Australia as
a glider tug is spinning the prop (via Blanton type PSRU) originally
used by the Pawnee when it had it's original engine which I believe
was an 0-470. It's spinning it at **exactly** the same prop rpm the
0-470 spun it. What does that tell you about power?

But it uses way less gas doing it.

Before BOb steps in and makes a comment, let me add that most of the
reason for the reduction in fuel burn is due to the method of flying
and the fuel mixture. The tug hauls the glider up to it's drop point,
then closes the throttle to idle and returns to the field with the
engine staying at idle the whole way. When the 0-470 was used, the
throttle was never closed for descent (shock cooling doncha know) and
who knows if the mixture was leaned during the return.

In addition, it's possible that the carburator mixture runs normally
more lean than the carburator mixture at full rich with the 0-470.
This is possible with the Ford because variable automatic timing can
still be used.

Magneto timing must be preset at around 26 degrees before top dead
center and does not move. In order to get the Peak Pressure Point of
the combustion process to occur at 16 degrees past top dead center
(rather than closer to top dead center which increases pressure and
heat) the combustion process must be slowed somehow. Engineers
achieved this by making the mixture overrich for takeoff and climb.

But since the Ford engine can vary the timing automatically (if the
builder uses a distributer or electronic ignition that allows this),
the timing is always where it needs to be to have the PPP occur where
it needs to for proper engine power. An overly rich mixture is not
necessary to achieve this.

Corky Scott