The more I think about it, the more logical it seems the buildup is a
combination
of blowby gases and some of the activated charcoal (carbon) from the vapor
recovery system. It ends up in the intake system since it's the source for the
vacuum for the vacuum controls used in the engine and it's downstream of the
PCV valve.
It's interesting that this crud is generally referred to as "carbon," whereas a
lot
of the stuff in blowby gases is oil and combustions byproducts (including some
carbon, of course). It makes me think this "carbon buildup" is a known problem
in the auto industry and that the source, in part, is the carbon in the vacuum
canister.
A simple filter might eliminate this problem, but it might add $0.90 to the cost
of the car and you know the bean-counters won't allow that ;)
Then again, maybe people just refer to any black crud in an engine as "carbon."
bs
********************************************
Bob Spidell San Jose, CA bspidell@comcast.net
'67 Austin-Healey 3000 '56 Austin-Healey 100M
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Subject: Re: Carbon Buildup, was Re: question on C (neither L nor B)
> Bob, try as I might, I don't remember the cloud chamber experiment. Maybe my
>school was not
> progressive enough. Or I was out that day. (Maybe working on my car or
>something.)
>
> Anyway, thanks for the explanation. Certainly that stuff gets up there, and
>you are right about
> older cars: this does not happen on my '66 Sprite or my '70 MGB. The MG used
>to have some
> active pollution control stuff that disappeared over time, but then too,
>maybe SUs don't promote
> this phenomena.
>
> Curious, too, are my motorcycles. I have a 1981 Yamaha Virago and a 1990 HD
>Sportster. Both
> have variable venturi carburetors, and neither tend to have the buildup.
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