White soot on exhaust

While taking my new to me'62 Cessna 172 with an O-300 (with about 75
hours on it SMOH with Millenium cylinders), I decided to start leaning
as I should on my last flight.
During the next preflight I noticed a whitish soot around the exhaust
and on the cowl just adjacent to the stack during the preflight.
Looking up on r.a.o for "white exhaust soot" I came across posts from
several years ago about the white soot being a side effect of leaning.

Does this sound right?
Am I leaning too much? (I'm still trying to figure out the lean and
rich of peak thing, especially for this particular airplane that I
have about 18 hours in).

Thanks,
Ryan Wubben
Madison, WI

I think you are leaning too much, but you might also want to remove the cowl
and look around the valves for similar soot leading away from them. If you
have a leaky valve you will sooner or later get a cracked cylinder.

The white soot is from the Lead in the fuel. If you run too rich or
are burning oil you will not see the white deposits only black soot.
In this case a white deposit is a GOOD thing.

A long long time ago you looked at the exhaust pipe of a car to see if
it was burning oil. If it was white you had a good engine. Then came
unleaded fuel and now all look black.

On 17 Apr 2004 20:28:34 -0700, (R. Wubben) wrote:

While taking my new to me'62 Cessna 172 with an O-300 (with about 75
hours on it SMOH with Millenium cylinders), I decided to start leaning
as I should on my last flight.
During the next preflight I noticed a whitish soot around the exhaust
and on the cowl just adjacent to the stack during the preflight.
Looking up on r.a.o for "white exhaust soot" I came across posts from
several years ago about the white soot being a side effect of leaning.

Does this sound right?
Am I leaning too much? (I'm still trying to figure out the lean and
rich of peak thing, especially for this particular airplane that I
have about 18 hours in).

Thanks,
Ryan Wubben
Madison, WI

I fly a 172 with an 0300D
Last summer I purchased an EI Engine monitor.
It monitors EGT and CHT on all 6, plus several other functions.
After purchasing it, it led me to a problem valve, and it taught me how
to lean my particular engine in every phase of flight.
It has given me a confidence in my engine that I never had before.
I strongly suggest that you invesigate one as the next purchase for your
aeroplane

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument
Cessna 172H C-GICE

On 17 Apr 2004 20:28:34 -0700, (R. Wubben) wrote:

While taking my new to me'62 Cessna 172 with an O-300 (with about 75
hours on it SMOH with Millenium cylinders), I decided to start leaning
as I should on my last flight.
During the next preflight I noticed a whitish soot around the exhaust
and on the cowl just adjacent to the stack during the preflight.
Looking up on r.a.o for "white exhaust soot" I came across posts from
several years ago about the white soot being a side effect of leaning.

Does this sound right?
Am I leaning too much? (I'm still trying to figure out the lean and
rich of peak thing, especially for this particular airplane that I
have about 18 hours in).

Thanks,
Ryan Wubben
Madison, WI

one of the beautiful things about classical Avgas is that you can get
an after flight appraisal of the engine. the burning of the tetraethyl
lead is what gives the coloured exhaust.
black is running rich
mid grey is burning perfect
lighter grey through to white is burning lean.

on my little Continental O-200 I just lean to peak revs on the tacho
and I get a beautiful mid grey exhaust.
if you climb or descend by more than a thousand ft then check the
mixture again.

works for me
Stealth Pilot
Australia