Flight training forum because it is more of an operator's than a maintenance issue, because it is training, and because most of piston GA is either FTUs or private owners who are recent students.

E Series O-320s are my favorite..... though I had one stuck valve on one that was because of using MOGAS. We also had an A Series on a Citabria that blew a rocker shaft boss on takeoff..... never saw that before. We did the jug change in two hours on the ramp in Salmon Arm.

O-320 H2ADs are junk, so are the 76 Series O-360s (had a bad camshaft on one of those too).

Why would mogas result in a stuck valve? I thought the lack of lead would reduce the chance of sticking exhaust valves, as long as you lean properly.

It is Mike Busch's opinion that when we
finally stop running leaded gas in our
little Lycomings and Continentals, that
they will run a lot better.

As someone who has scraped a lot of
lead deposits out of engines, I am
inclined to agree with him.

Note that exhaust valve stem-to-guide
clearance decreases because of:

1) carbon deposits on valve stem
2) lead deposits on valve guide
3) valve guide being at lower dimensional limit

and I'm sure that there is variation
in valve stem diameter, too.

PS There is no "owners" or "operation"
forum. This really isn't maintenance.

CpnCrunch wrote:Why would mogas result in a stuck valve? I thought the lack of lead would reduce the chance of sticking exhaust valves, as long as you lean properly.

I'm not sure why..... that is what the engine shop owner said. But we haven't used that shop in ten years because of various issues so it is possible he didn't know what he was talking about. The engine had about 400 hours on it, Millenium cylinders (yuck) and had run on nothing but MOGAS.

It was my understanding that the valves need a little bit of lead to operate correctly.... which is why guys usually run about a 25% mix of AVGAS.... or fill up with 100LL on the $500 hamburger runs.

Millenium cylinders (yuck)

Yeah, no kidding. I saw a stuck valve on
one of those (not my aircraft) a while back.

Measured the valve guide, it was at the
very bottom of the table of limits. I honed
it out to the middle. Been running perfectly
ever since.

Check the Lyc table of limits for helicopter
valve guides. Hmmm. How does the engine
know the blades are horizontal instead of
vertical?

Thanks for posting all the info Colonel on operating procedures. As a white shirt gold bar guy this info is useful. I get to put a few hours every year on my friends PA 12 and 182. Your info acts as a good refresher on proper operating techniques for these engines.

Why are the Contis so much more resistant to corrosion than the Lycomings? Choices of alloys, or some other factors?

I'm sure the good Colonel will correct me if I've got anything wrong here.

The Continentals have the camshaft below the crankshaft and get splash lubricated as soon as the engine starts turning.

Lycomings have the camshaft above the crankshaft. The oil drains away, it doesn't start getting lubricated till the oil pressure builds in the oil galleys. Things like Camgaurd are helpful because it helps keep an oil film on the cam and lifter surfaces for longer.

Gerry

Yeah, the camshaft placement sounds good,
but I can't help but thinking there's some
metallurgy involved, too.

Recall Lycoming's nasty legal fight with their
crankshaft supplier over vanadium with 4340,
for example.

Anyways, Lycoming cam & lifter spalling is
such a huge problem (esp in infrequently flown
private aircraft, worse in humid & salty areas)
Lycoming has gone to roller lifters. Of course,
you now have 12 additional bearings (at $260
each which MUST be replaced w/new at overhaul)
to fail in your engine. That's over $3,000 right
there, just for roller bearings at overhaul.

Camgaurd are helpful because it helps keep an oil film on the cam and lifter surfaces for longer

This may seem like a really weird choice for
the Canadian climate, but these days I'm
running Aeroshell W100 with Camguard,
which should stick to the cam lobes.

Needs pre-heating, of course, and congeals
at -20C but you have to choose the lesser
of two evils.

Recall that 2F is W100 with corrosion inhibiting
additives which is similar to W100 with Camguard.
Yes, you can fly 2F for 100 hrs during TBO, but
it builds carbon. Again, you choose the lesser
of two evils.

Does this camguard stuff also help prevent cylinder corrosion?

LnS.

Yup.

"Yes, you can fly 2F for 100 hrs during TBO, but
it builds carbon. Again, you choose the lesser
of two evils."

I ran on 2F last summer ... didn't note anything all that different ... Since I would run W100 + CamGuard otherwise, this is an interesting comment.

So 2F builds more carbon than the alternative? My spark plugs looked about the same as in previous years ... maybe the valves are getting gunked up. Still I'd rather that than corrosion ... ?

Gonna start my annual tomorrow ... but I did my first flight of the season already .. started on the first try, if with some hesitation at first, but after months on the ground (fully pickled properly) it's always nice to see ...

Instead of 2F, a better alternative to
prevent internal engine corrosion is
Aeroshell W100 plus 5% Camguard.

Spend an hour Googling. Don't take
my word for it. Don't take anyone's
word for it. Lab results are king.
Everything else is nonsense.

If you are not going to fly for a while,
drain your oil, change the oil filter,
put Aeroshell W100 plus 7 to 8%
Camguard in it, and fly it, then
park it. Mist the cylinders, dessicant
spark plugs, and dessicant in the
intake and exhaust as required for
the length of time in storage, and
ambient conditions.

maybe the valves are getting gunked up. Still I'd rather that than corrosion

You can clean the valves and guides
in a day if you can find an AME that
knows how. You can't change a cam
and lifters in a day.

That said, fresh 2F in the engine is
better than old oil. But there are now
better alternatives than 2F.