I happens to have a lot of faith in GM engines. They , like
  everything else, are not perfect. Chevy had camshaft problems in the
  distance past,and the timing chain is the first thing you dump when
  you hop up the engines, gears are much more reliable.However it is
  the Chryslers that like to jump teeth with their plastic gears etc.
  Fords had problems in their V8's a decade ago with too few threads
  holding the spark plugs.Aircraft engines are made with the finest
  steel and techniques available...................in the 1940's!! If
  I have such a high opinion of the word "certified" I would not be
  looking at alternate engines.They published my letter in the latest
  Flying mag. on that subject. Another reason for the nickel content
  is for a bit better corrosion resistance, which a/c have more than
  many cars. The nickel content also add some toughness, but I don't
  think they have any where near as much as in amour plating.

  Auto engines had incremental improvements  through the years, while
  aircraft engines are at a stand still, and still have lead in the
  gas. The auto industry, easily 100 times the size, within a time
  span of 3 years, had the lead removed starting in 1975?Basically
  with hardened valve seats and to get the necessary octane with more
  refining without the lead. Now they use ethanol.They had incentive
  from governments, especially Calif.

  A 400 HP engine only use a small fraction on the highway, that is no
  indication of the engine's toughness. A Chevy small block 350 cubic inch
  can easily put out twice that or even more in dragster applications
  where the engine life is 1 mile.

  I heard of how they pushed these engines during endurance testings, some
  with pictures of the turbo glowing red hot.So a race modified 400 HP
  Chevy LS engine at 350 HP cruise would easily outlast the standard 2000
  hr. TBO , the TBO times could rival that of a PT-6! I think the % of
  certified engines that made it to TBO is around 5% or less.
  But the piston engine do have several inherit disadvantages, compare
  with rotary and turbines, more part count, liquid cooling, and the re
  drive, one more thing to go wrong.

  The re drive  I think is only troublesome for the smaller HP
  applications, where there are more space, weight  and budget
  constraints. Even Rotex, with their engineer resources available to
  them, had their shares of AD's.By the time you get to 300 HP,  I
  don't hear as much complaints.All turbines have re drives, for prop,
  fan or accessories, yet the PT-6 have a reputation for reliability.
  One thing the Viking engines(and Rotex) taught me, they use Evans
  coolant. This stuff boil at 375F, a significant margin in borderline
  detonation cases in boosted engines. That means I only need a
  minimal amount of pressure (0-5 Psi?) to aid circulation and to
  forget the pressure for raising the boiling point.That increase
  reliability. The engine may run a bit hotter. Tony Lam

  A race modified  V8 is lucky to last a 24 hour race.
  It took GM several years on a Le Mans programed dyno to get a Chevy
  V8 to last 24 hours. We had to back off on the sprint car power red
  line. As it was, GM used all aircraft qulity parts. The engines were
  then worth over $100,000 in today's dollar. The fundamental problem
  is inadequate bore spacing and the V8 configuration,

  http://www.rotaryeng.net/DS-smith-art.pdf

  Smithsonian Air & Space magazine article "Power Struggle" by Don
  Sherman, January 1997, page 72. Excellent ten page  article (with
  many pictures) about auto engines in airplanes. A brief history of
  all auto engines in airplanes and a more detailed history of the
  twenty year, twenty million dollar  development of the Chevy V8
  based, all aluminum Orenda liquid cooled aircraft engine. At this
  time (Jan 1997) and well after the article was written the engine
  failed its FAA 150 hour full power certification test due to a
  crankshaft problem after 20 years of very expensive development.
  It was finally certified in 1998 by Transport Canada.

  Extensive changes have been made to the basic Chevy big block engine
  including a parallel cooling system with dual coolant pumps as
  opposed to the serial cooling system with single pump as typically
  found in automotive engines. Parallel cooling systems were
  considered to be essential in the 1920's on liquid cooled aircraft
  engines.

  Engine length is almost everything to a car designer. Engine cooling
  compromises are made by simezing the cylinder walls in automotive
  engines. Crankshaft life at high continuous power is compromised by
  shortening the length, leaving too little room for adequate size
  journal fillet radii. In my opinion this engine will not be
  successful until it is re-designed from a clean sheet of paper to be
  a real aircraft engine. If that happens they might as well go to a
  horizontal opposed configuration for lighter weight.

  Orenda is now in the process of moving the project to Nova Scotia
  and injecting another 32 million dollars of mostly Canadian
  government money. They are also attempting to market the engine to
  the homebuilt market. I don't expect many takers at over $100K per engine.

  Recently Lancair gave up after spending a lot of money installing
  the engine in a special airplane called the Lancair Tigress.
  The engine and the Tigress were donated to the EAA museum as
  a tax write off.

  The Orenda company is now bankrupt.

  http://www.rotaryeng.net/DS-smith-art.pdf

  Paul Lamar



  Tony,
  All of the big three used nylon on the camshaft timing gears to reduce
 NVH,
 and they all fail in time due to the nylon becoming brittle. When this
 happens
 they ALL come out of time and depending on the circumstances may destroy
 the
 engine.

  Drag race engines can put out phenominal power for a short time and then
 they are rebuilt. Road race engines have to last longer and thus are not
 built
 to rev as high to get the HP. Endurance race engines are pretty much spent
 when done a 24 Hr race.

  This all boils down to design usage and duty cycles. When you move outside
 the design duty cycle you have to re-engineer most everything. The internal
 forces on a reciprocating piston engine are extreme when using a high duty
 cycle. To make an engine last for 24 hours at race power requires a lot of
 extremely expensive components. Forged crankshafts, connecting rods,
 pistons,
 valves to name a few. When Chevy built the endurance engines, the titanium
 rods is one part that got attention.

  The Ford that blew the plugs out are not an ancient fact. They were on the
 earlier Mod motors of 10 to 15 years ago. All have screwed up on the
 engineering at some time or another. Some may be attributable to the bean
 counters getting their noses in the engineering department where they
 should
 not be allowed.

  If YOU feel comfortable with an automotive piston engine conversion in an
 experimental AC, you are welcome to it. You can not use a crate engine as
 is
 from the factories as they will not usually stand up to the HIGH duty
 cycle.
 As usual there are exceptions but in this case they will be few and far
 between!
  In my opinion the ONLY ACCEPTABLE engine alternative to certified is a
 rotary engine due to the low internal stresses experienced.

 Dale Davies

                I will have to agree with Dale. Just as a matter of
experience I have never seen a GM engine that I have operated in the last
20 years hold up past 100K miles where Nissan and Toyota are just getting
there second wind at 250K miles. How does that relate to rotary engines? It
really doesn't directly but it speaks to reliability, and I would never
trust a GM engine to last over a few hundred hours in an airplane at 70%
power or more with the experience I have with them at 40% power or less on
the ground. The rotary engine is the only engine I would trust in the air
because of it's simple but robust design. I'm convinced it is the safest
combustible engine design you can have in the air. Of course this is just
my humble opinion, please feel free for anyone else to disagree, it is just
I have seen several GM engines and reduction gear combinations fail and
witnessed one death personally of someone I knew and liked, so I have a
strong opinion about the subject.
James Ealey

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