General Aviation News - 21 June 2018

June 21, 2018 http://www.GeneralAviationNews.com — facebook.com/ganews 17

when converted to an O-200, caused an
oil geyser.
But the cause was never revealed. In-
spection of the dismantled case didn’t
reveal any obvious clues and, to some
degree, the problem defies all mechanical
logic in the first place.
As the months rolled past, sort of like
Big Foot sightings, I heard rumors of oth-
er geyser sightings.
But they were always like the car-
toon character SpongeBob SquarePants’
knowledge of Sea Bears: “Sea bears are
no laughing matter. Why, once I met this
guy, who knew this guy, who knew this
guy, who knew this guy, who knew this
guy, who knew this guy...who knew this
guy’s cousin...”

In the same way I’d get emails from

pilots and mechanics, who while never

having seen an oil geyser themselves, met

this guy, who knew this guy, who knew

this guy, who knew this guy, who knew

this guy’s cousin, who had seen one.

Still, it was nice to know that my issue,

while exceedingly rare, was not, appar-

ently, one of a kind.

Excuse me while I step

outside and scream

Most maddeningly in all of this is that

I later learned that when our original en-

gine was cracked open, it was found to be

“in pretty good shape.”

So really, all of this was for nothing,

while causing me to miss out on half the

2017 race season. And perhaps the Gold.

So now that we’re up and running

again, what about the 2018 racing season?

In the spring (between the leaking gas

tank and the exhaust issues) I threw my

hat in the ring, but as my plane problems

mounted, I took my hat back out of the

ring before the first race.

Partly it was the mounting repair costs,

but mostly, given all that’s happened, I’ve

simply lost trust in my trusty steed, and

need to regain it before I travel thousands

of miles in her — much less race her.

Still, something must have caused the

original problem, right?

What do I personally think caused it?

Many knowledgeable mechanics wrote

in (thank you, all) and felt our issue was

caused by the wrong length of breather

inlet, but that isn’t our smoking gun. We

had the proper modification all along.

So what else could cause it?

To my mind, the best theory to date

deals with the internal structure of the en-

gine. I’m told that inside the case there’s a

structure similar to a rib that adds strength

to the case wall. This rib is on both sides

of the case, but the two ribs don’t quite

meet at the top.

In other words, there’s some open space

— a gap — between them. How much of

a gap? Well, that’s where this theory gets

interesting.

Apparently, this gap is one of the few

internal structures that doesn’t have a spe-

cific published tolerance from Continen-

tal, as it doesn’t have a mechanical func-

tion, and doesn’t interact with the moving

parts.

As it so happens, the opening between

the two sides is less on the case we pur-

chased than it was on Race 53’s original

case, which we’re back to using now.

My team thinks that in some way that

they can’t clearly imagine or even fully

articulate to me, this is the root cause of

the problem. Perhaps, they say, the gap

didn’t matter with the original crankshaft,

but for some reason it does matter with

the slightly larger O-200 crank.

The thinking further goes that, as it

“didn’t matter” in the original configu-

ration, perhaps the size of the gap might

have varied pretty widely from engine

to engine when they were manufactured,

without triggering any quality control

alarms, nor did the variable gaps cause

any operational issues in the field with the

original cranks.

But maybe, just maybe, once modified,

the size of the gap matters. But if true,

shouldn’t more people be having prob-

lems?

Not necessarily, fans of this explanation

argue.

What if, for instance, one in a thousand

of the C-85s had this tight gap? No one

knows how many C-85s have been con-

verted to O-200 strokers under the supple-

mental type certificate (STC) that allows

it, but it doesn’t take much imagination to

see how an uncommonly tight gap would

rarely meet up with a conversion.

In other words, there might only be a

few C-85s out there that can’t be success-

fully converted, and I had the bum luck

to buy one.

They are rare — rare enough to have

been missed as a possibility when the

STC was granted — but still existing in

just large enough numbers to result in the

occasional Big Foot sighting.

And one ruined underdog race season

for yours truly.

But it’s only a theory, and I don’t know

that this is what really happened.

For all I know, Race 53, like her living

machine namesake, has a mind of her own

and just didn’t want to part with her origi-

nal engine.

In the end, all I know is that we’ll never

know the rest of the story.

Photo by William E. Dubois

Striking oil is never a good thing when you are an air- Photo by William E. Dubois

plane owner. The engine problems fixed, Race 53 sprung

a new oil leak all over her hangar floor.

Drips of oil from the quick drain valve on the sump

caused the hangar floor oil slick.

Strategically placed paper towels helped to trace the latest oil leak around the first of the year, but the trophy shelf
in the background isn’t looking like it will have new additions anytime soon.

Photo by William E. Dubois