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From: rls@ihu1g.UUCP (r.l. schieve)
Newsgroups: net.auto.tech
Subject: Re: causes of blue smoke:  ring wear vs. valve seal wear
Message-ID: <728@ihu1g.UUCP>
Date: Mon, 11-Nov-85 09:01:31 EST
Article-I.D.: ihu1g.728
Posted: Mon Nov 11 09:01:31 1985
Date-Received: Tue, 12-Nov-85 04:25:44 EST
References: <1278@ihuxi.UUCP> <318@watmum.UUCP>
Distribution: net
Organization: AT&T Bell Laboratories
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> Many, many people have posted articles to the effect that blue smoke
> on closing the throttle is a symptom of valve-guide wear, not ring
> wear.  I think these statements are misleading.
> 
> In my experience, the symptoms are exactly consistent with ring wear.
.........
> I have not conducted a statistically valid survey (I am sure the other
> posters have not, either), but in my experience high oil consumption
> is almost ALWAYS caused by ring wear and almost NEVER caused by valve
> wear (5-0 on cars I have actually repaired).
................
> I won't argue too strongly against replacing both the rings and the
> valve guides, but I think it is holding out false hope to suggest
> that fixing the valves alone is likely to cure heavy oil consumption.
............

One confusing part of the above article is whether valve guide wear
or valve seal wear is being discussed.  My own experiences, working
with cars that are reasonably maintained, (oil changed regularly) is
that rings are almost never the problem but valve SEALS very often
are.  Whenever my 1971 GTO started going through more than 1 quart of
oil in 1000 miles, I knew it was time to replace the valve seals.  One
time I took the heads off thinking the valve guides were bad causing
the seals to self destruct.  The shop asked me why I bothered to bring
the heads in as the valves were fine, just new seals needed.  They
recommended teflon seals for replacements.

My 1980 Turbo Mustang, used to go through valve seals constantly due
to the higher engine temperatures.  The seals got brittle and
cracked.  The second set went bad so quickly that I let a mechanic
convince me I had a cracked ring and I didn't recheck to valve seals
until I had the engine disassembled.  No cracked piston rings, but
lots of cracked valve seals, and lots of cussing at the mechanic.
The engine didn't even burn the oil, it got right past the seals
directly into the exhaust manifold.  3 out of 4 exhaust port were wet
with oil.

My advice, try the valve seals first!!!!!

					Rick Schieve
					...ihnp4!ihu1g!rls