pragmatist wrote:

John Thompson wrote in message ...
Corky,
I think one of the biggest roadblocks in autoconversions is the lack of
"cookbooks". Instructions that cover things like that "stud stretching"
tip, why you might want to use this camshaft, or replace this part or
other, lifter bearing replacement, etc. and where to get them.

SNIP

John

Amen to that, but what scares me about auto conversions is the that
the design parameters for the auto engine are based on 25-30% constant
power at hiway cruise.
The reliability of the engine in automotive use is therefore not a
meaningful indication of fitness for flight.
Even with the engine blueprinted and a beefed up cooling system and
oil cooler added, when you run that engine at constant 75-80% power in
an aircraft you are likely to have 'hot spots` in there somewhere
which can play hell with reliability.
Do a lot of base testing Corky, and good luck to ya.

A lot of this seems to me to depend upon the question of: 75% of WHAT?

75% of the rated power of the 'truck' version of the engine will probably
be around 0.5 horsepower per cubic inch of piston displacement. That is
well within reason for a liquid cooled engine, and could give excellent
service life. However, a friend who is a mechanic (automotive) has
cautioned me that RPM is important! It seems that something near the
RPM at which maximum power is produced, again on the 'truck' version, is
probably acceptable; and in no case should the engine operate at high
sustained power levels below the RPM at which peak torque occurs.

I suspect, but don't know, that engines commonly used in stationary and
truck service probably have recommendations available regarding the
acceptable relationship of rotational speed and sustained power output;
and that where such manufacturer's recommendations are available, they
should be treated as gospel.

Although I can't give you any useful experience as of yet, a realistic
power expectation and operation in the correct speed range should give
you a "poor man's Merlin." :-)

Peter