F

fazlo

Member
Hi there!
After a 2 hour flight at FL95 I was surprised to find a fairly sizable deposit of white/grey ashes when rubbing my finger at the end of one of the exhaust pipes(and not both). The engine is a carbureted O-320. Anyone has an idea of where does this come from? Thx for tips.
 
white/gray color

I had always been told if you run your finger in your exhaust pipe and there is white/gray dust on it, that means you are running your engine the way it should be run.

Can anyone verify or debunk that?
 
If you're only getting lead deposits on one pipe that means one of the cylinders on that side of the crossover is pumping a bit of oil past the rings which is not unusual.

Grey pipes are good if running 100LL.
 
Need an exhaust reader

Bob can you read these deposits? On recent loooong trip I burned all kinds of fuel. Mostly avgas, then some mogas, one load of ethanol laced 87, then avgas again. What are those brownish streaks?










 
Just a wild maybe but iron sulfate? A solid material resulting from sulfur in fuel combined with condensed exhaust water forming sulfuric acid that dissolves minute amounts of Fe in the exhaust pipe then, evaporates as the pipes warm and leave the streaks. The change in color where the streaks begin seem to be the hot zone of the exhaust and the border is where the air blast from ahead has cooled that part of the pipe, the tip.

If this is correct then warm water will completely dissolve it.

There used to be much more sulfur in fuels than today. I have seen something similar in diesel exhaust pipes using high sulfur fuels across an oxidation catalyst in below zero air.

Or- it could be something else entirely and this is all my vivid imagination.

Welcome back Vlad!
 
Guide wear...oil getting thru the valve guides. Pretty normal to see.

Oxidized oil will be coffee-with-creamer colored.
 
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