IO 360 Power down (danger, long, rambling post!)

"Jim Harper" wrote in message
om...
Hi, group. I've come to this august assembelage of persons to ask for
ideas, and to discuss a few of mine. I am the proud owner and flyer of
a lovely, new, RV 8A. Alas, I am not the builder, but as I am sure you
know, owning one begins the process of working with one...

At any rate, we have around 135 hours on this machine. Engine is an
IO-360-A1B6 with one Plasma ignition, one Bendix mag, Gami injectors,
Aero Composites CS prop, stock Van's intake with K&N filter on the
left front baffle shelf. Since the airplane started its flying life,
itsbeen power down. The engine is one of those Bulldog engines
imported from England. It has around 900 hours total, and is fresh
(just before installation) off of an overhaul. Compressions are fine,
plugs look good and I am taking good care of it.

Van's says a 200 horsepower RV8A will cruise at 210mph at 75% power at
8000 feet. Book says it will climb at 2500 fpm at 1500 pounds.

Mine cruises at 182mph and climbs at 1800 fpm. Now, nothing wrong with
that performance, but still and all...The airplane is straight and
slick. No unusual drag makers. It would seem that I am missing around
25 or so horsepower.

snip

Any of y'all have any OTHER suggestions? The intake manifold would
look to be OK, no holes or the like.

Thanks for sharing my quandry.

Jim

How about a bad camshaft or follower? You could pull the valve covers and
plugs, then rotate the engine by hand and measure the movement of the rocker
arms to see if you have a worn cam lobe or follower. This is a simple way
to determine if there is a valve that doesn't get the same lift as the
others...

By the way, do you have RPM and MP data on the engine? Are you gettting the
reduced performance you quote when running at 75% per the lycoming
rpm/mp/temp charts?

Is it possible that your tach is off or your MP is low because of a clogged
air filter or some other induction problem?

KB

"Kyle Boatright" wrote in message ...

How about a bad camshaft or follower? You could pull the valve covers and
plugs, then rotate the engine by hand and measure the movement of the rocker
arms to see if you have a worn cam lobe or follower. This is a simple way
to determine if there is a valve that doesn't get the same lift as the
others...

By the way, do you have RPM and MP data on the engine? Are you gettting the
reduced performance you quote when running at 75% per the lycoming
rpm/mp/temp charts?

Is it possible that your tach is off or your MP is low because of a clogged
air filter or some other induction problem?

KB


Thanks to everyone, so far for the excellent suggestions. Kyle: we are
gonna check for valve timing, and will pursue looking for a worn cam
lobe or follower. Good suggestion, thanks.

My tach has been confirmed by an optical tach, so those are both spot
on. MP? One of the things we are wondering about is an induction
problem, but so far that doesn't look likley. Regarding your comment
about RPM/MP data. Yes, I have RPM and MP data, and can cruise at the
appropriate RPM and MP for 75% power at a given altitude and
temperature. However, if the engine was somehow "derated" to 180 HP,
wouldn't I just be getting 75% of 180HP? The constant speed prop is
going to adapt to the power output to maintain the appropriate RPM,
and the MP is just the MP.

One of the things that lead me to this group was the comment elsewhere
that IO 360 were hot running engines. Mine is pretty cool running.
Hence my suspicion that I am not producing the horsepower!

Thanks again, all.

One hopes we'll have an answer in a few days!

Jim

"Jim Harper" wrote in message
om...
"Kyle Boatright" wrote in message
...

How about a bad camshaft or follower? You could pull the valve covers
and
plugs, then rotate the engine by hand and measure the movement of the
rocker
arms to see if you have a worn cam lobe or follower. This is a simple
way
to determine if there is a valve that doesn't get the same lift as the
others...

By the way, do you have RPM and MP data on the engine? Are you gettting
the
reduced performance you quote when running at 75% per the lycoming
rpm/mp/temp charts?

Is it possible that your tach is off or your MP is low because of a
clogged
air filter or some other induction problem?

KB


Thanks to everyone, so far for the excellent suggestions. Kyle: we are
gonna check for valve timing, and will pursue looking for a worn cam
lobe or follower. Good suggestion, thanks.

My tach has been confirmed by an optical tach, so those are both spot
on. MP? One of the things we are wondering about is an induction
problem, but so far that doesn't look likley. Regarding your comment
about RPM/MP data. Yes, I have RPM and MP data, and can cruise at the
appropriate RPM and MP for 75% power at a given altitude and
temperature. However, if the engine was somehow "derated" to 180 HP,
wouldn't I just be getting 75% of 180HP? The constant speed prop is
going to adapt to the power output to maintain the appropriate RPM,
and the MP is just the MP.

One of the things that lead me to this group was the comment elsewhere
that IO 360 were hot running engines. Mine is pretty cool running.
Hence my suspicion that I am not producing the horsepower!

I was talking about a six-cylinder Teledyne Continental IO-360 engine in
the thread about cylinders running hot because they had flashing between the
fins, if you were referring to my comment. Of course, the Lycoming IO-360
is a four-cylinder engine.

As to your engine start troubleshooting by the shop manual --- static runup,
first.

Best of luck and keep us posted on what your findings are.


Thanks again, all.

One hopes we'll have an answer in a few days!

Jim