Cleaning Spark Plugs is a Simple Job...

Lately I had noticed just a smidge of roughness in the engine. Not a
roughness, really, but a slight vibration, maybe a little, tiny, occasional
miss? It was not detectable by anyone except someone who flew the plane as
often as I do (and, in fact, Mary often couldn't sense it), but it was
definitely there.

It had been 150 or so hours since we last had our spark plugs cleaned and
gapped -- a good 50 hours past optimal, according to my A&P (although
burning unleaded mogas extends that interim dramatically) -- and I had the
day off with which to test my brand new "spark plug cleaning/gapping kit"
from Aircraft Spruce. I was determined that, for once, I wouldn't bug my
mechanic about stupid, "grunt work" -- I would do it myself!

"As long as I was at it" I decided to change the oil and filter, too. We
only had 29 hours on the oil, but it had seen some hard, hot, summer
hours -- and we like to aim for every 25 hours, anyway. And then, since I
was getting all greasy anyway, I figured it was a good day to put a new
battery in the "Mighty Grape" -- our fuel hauler which Mary was forced to be
push-start last week, due to low electrons.

I, of course, figured cleaning and gapping the plugs would take an hour,
maybe two, tops. As always, I was off by a factor of four. The first thing
I realized was that I had NO idea how to gap the plugs using my new gapping
tool. It was totally different from the automotive feeler gauges I had used
in the past, as was the "feeler gauge" they supplied that looked more like a
dental tool with short lengths of guitar strings sticking out of both ends.
What the hell was I supposed to do with *that*?

No problem -- the kit (which came in a VERY handsome walnut box, BTW) came
with instructions. Unfortunately, said instructions had been xeroxed from
another xerox, which was probably copied from an old mimeograph back in the
1960s. I could barely make out every other word, and nothing really made
sense.

Staring ruefully at that beautiful, useless walnut box, I reluctantly set
off for my mechanic, kit in hand, feeling sheepish and silly. I mean,
really -- all I was doing was trying to gap the stupid spark plugs!

Always a gentleman, he cordially showed me how to work my new tools -- and
then showed me how to clean the plugs with a dental pick. Of course, this
looked like it might take all day, so he then showed me how to use his cool
little plug cleaner -- a Radio Shack engraver with a special attachment for
getting down around the electrodes. It gently vibrates (as all engravers
do) the holy hell out of the crap and corruption that builds up in there,
allowing for proper inspection of the porcelain.

Of course, the plugs were still covered with gray baked-on stuff, which can
be cleaned off with an emery cloth and some patience. This, of course,
looked like it might take all day, so he patiently showed me how to use his
cool spark plug sand-blaster, where all I had to do was stick the plug in
the hole and push a button. 15 seconds later, voila! The plug looked like
new!

Then, of course, he showed me how to get the old, hardened thread anti-seize
compound out of the threads, using a dental pick and a wire brush. This, of
course, looked like it might take all day, so he patiently showed me how to
use his bench grinder's wire brush wheel to clean all the old gook out of
the threads.

And, finally, he recommended rinsing the newly cleaned plugs in solvent
before gapping them. This, of course, looked like it might take all day, so
he showed me how to rinse them using his motorized parts washer, and dry
them off with a blast or two of compressed air.

Then it was time to actually gap the plugs. The guitar string thingy turned
out to not be a gapping tool at all, but a gap measuring tool. The one side
was a thinner wire (14?) that should pass between the sides and the
electrode when the plug is gapped correctly. The other side was a thicker
wire (18?) which should NOT pass between the sides and the electrode when
the plug was gapped properly. Thus, by the process of elimination, using
the little gap setting tool (a circular collar that threads onto the plug,
with two opposing thumbscrews that squish the sides in closer to the
electrode) you could set the gap more or less properly.

Why this is the accepted way to do this, instead of the automotive feeler
gauge tool method, I don't know. But, after a little practice, it worked.

Then it was time to rotate the plugs. I had fashioned a box with
appropriately labeled holes for all 12 plugs, and my A&P showed me the
accepted way of rotating the plugs. He admitted that there may not be a lot
of logic or utility to the practice anymore, but he advised doing it anyway.

Then it was back to the plane.

By now the oil had fully drained, and the usual hanger bums had gathered to
see what was going on. I became tied up with them in conversation, so Mary
proceeded to remove the oil filter -- a first for her. She, of course, as
we all do the first few times, managed to dump oil all over the place. The
hanger bums were beside themselves with awe (at the fact that my wife was
actually willing to *do* any of this stuff) and laughter, as she tried
desperately to do a three-handed job with only two. But she eventually
wrestled it to the ground...

Putting the plugs back in required using my other new tool -- a gigantic
Craftsman torque wrench. I had my A&P set the torque properly the first
time, just to make sure I wasn't mis-reading the danged thing and twisting
something off inside the engine. Unfortunately, I discovered that my torque
wrench was a 3/8 inch drive, and my spark plug socket was a 1/2 inch
drive -- and I didn't have an adaptor to make them work together. So, off
to the local hardware store to fetch the little bugger, and -- 20 minutes
later -- I was finally able to properly reinstall all 12 plugs, six JPI
temperature probes, six washers, and 12 wires.

Then I installed the new oil filter, and Mary added 12 quarts of Aeroshell
oil.

We then, of course, had to reattach the cowlings and do a ground run,
testing for leaks. Everything ran perfectly, without leaks, and -- although
we didn't fly, due to high winds -- I think the engine ran noticeably
smoother.

In the end, the job(s) took about 5 hours, although we wasted a lot of time
shooting the breeze. My goal of independence from my mechanic turned out to
be a complete farce, as I ended up needing his advice and tools at every
step of the job. While it's true that in the future this won't be the case,
advice-wise, using his tools sure made the job easier and the results of
higher quality -- and it doesn't make any sense for me to buy all of those
things for the twice a year I need to do this. So, I suspect I'll not be
declaring basic maintenance independence just yet...

As usual, he would not accept any money for all of his help. We ended up
buying a case of Coke for his shop, simply because that's the only thing he
said he needed -- and we felt we had to give him *something*. He's a great
guy, but I sure wish I didn't need him for such a "simple" job...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

("Jay Honeck" wrote)
Lately I had noticed just a smidge of roughness in the engine. Not a
roughness, really, but a slight vibration, maybe a little, tiny,
occasional miss? It was not detectable by anyone except someone who flew
the plane as often as I do (and, in fact, Mary often couldn't sense it),
but it was definitely there.


Oh my God, the prop!!


Montblack

Jay Honeck wrote:
Lately I had noticed just a smidge of roughness in the engine. Not a
roughness, really, but a slight vibration, maybe a little, tiny, occasional
miss? It was not detectable by anyone except someone who flew the plane as
often as I do (and, in fact, Mary often couldn't sense it), but it was
definitely there.

***Saga of changing oil, cleaning and gapping plugs deleted***

Jay, I'll wager that your roughness will still be there when you next
fly. I just went through this on an O320. I cleaned/gapped the plugs,
and this did not cure the roughness.

It turned out that my Slick Mags have 370 hours since new, and the
roughness resulted from the point gap in the Right Mag being too small.
The plastic block that opens the points had worn down to the point
where the point gap was reduced to ~0.006", instead of the specified
0.018".

This manifested as a slight roughness in flight, made more noticable by
shutting down the Left mag. The roughness was not noticable during a
run up (nor was there an asymetrical drop) .

Per the Slick SB, the mags are normally opened up at 500 hours, and the
point gap is set. Mine just happened to need this early...

Mike M.

Per the Slick SB, the mags are normally opened up at 500 hours, and the
point gap is set. Mine just happened to need this early...

You know, I've wondered about this. Our left mag shows a smidge more of a
drop than the right mag -- it's, again, probably not noticeable to someone
who doesn't fly the plane all the time.

What's involved with setting the mag point gap?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Oh my God, the prop!!

Funny you should mention that. It could, actually, *be* the prop -- but to
my ear it sounds more like a very slight engine roughness rather than a prop
imbalance.

Sometimes it's hard to separate the two -- and sounds have a funny way of
traveling.

For example, our Subaru Outback has developed a very annoying rattle in the
right rear that starts at around 50 mph. It's a harmonic rattle, and we've
looked at EVERYTHING trying to find something loose, to no avail. Yet,
clearly, there is something very loose, somewhere. Our best guess at this
point is that it's something inside the right rear door -- but I haven't had
time to rip it apart to see.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
Per the Slick SB, the mags are normally opened up at 500 hours, and the
point gap is set. Mine just happened to need this early...

You know, I've wondered about this. Our left mag shows a smidge more of a
drop than the right mag -- it's, again, probably not noticeable to someone
who doesn't fly the plane all the time.

What's involved with setting the mag point gap?

Talk to your A&P. Proceedure is specified in the Service Bulletin.
Mag(s) have to be removed, split, internally inspected (particularly
the impulse coupling), lubricated, both the E gap and points gap set,
new gaskets, reinstalled on the engine, and retimed.

Mike M.

: What's involved with setting the mag point gap?

Depends on the mag. I'm not familiar with slicks, but on my Bendix there
aren't quite enough adjustments to set everything. The wear of the points vs. the
plastic wear block is fixed by the points. If either is out of spec, new points are
required.

I'd agree with the checking of the internal mag timing (i.e. e-gap). If
you've got a few hundred hours on the mags and/or if it's had the external timing
adjusted, it may have worn a bit out of spec. We just did it on both our mags last
year. Again... it's Bendix.

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Did he also show you how to install new spark plug gaskets or re-anneal
the old ones?

Did he also show you how to install new spark plug gaskets or re-anneal
the old ones?

Yep.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
: Did he also show you how to install new spark plug gaskets or re-anneal
: the old ones?

: Yep.

Which reminds me... should one try to do that on the spark-plug thermocouples
for measureing CHT? It's always bothered me that they *replace* the original copper
gaskets.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************