Thanks. It doesn't smoke all of the time, just on the odd occasion. So the
rings are pretty good. The seals looked really good but I had new ones here
so I replaced them just to be safe. The buildup is actually white and hard
almost ceramic in consistency. There was actually very little carbon build-
up and the intake valves were pretty much free of this crud. Another oddity
is that only exhaust valve #4 had the buildup in the back side.
At 5:27 PM -0400 4/6/98, Ron Soave wrote:
>An idea from a non-expert (list join in at any time):
>As you know, the carbon is caused by oil, which in that location I would
>guess would be caused by either bad rings, or bad valve stem seals. With
>rings, you'd see blue smoke all the time, with seals, you'd see a puff of
>blue out the tailpipe on startup. On the back side of the valve like that,
>I'd guess that when you shut the engine down hot, some oil is leaking past
>the seal and coking on the back side of the valve, hence the puff at
>startup. Since the backside of the exhaust valves are hotter, the problem
>would manifest itself there first.
>Just a theory, but I'd check the seals.
>> From: robert weeks <email@example.com>
>> To: firstname.lastname@example.org
>> Subject: mystery valve buildup
>> Date: Monday, April 06, 1998 5:16 AM
>> I posted two photos of the head off my engine at:
>> There is an incrediable amount of buildup on the exhaust
>> valves for an head that only has 5-6 thousand miles on it.
>> The rattling sound that we thought was either a loose
>> seat or a bad bigend bearing was actually the crud on the
>> backside of exhaust valve #4 hitting the air injector.
>> If anyone has any ideas on how to avoid or lessen this
>> buildup I'd appreciate hearing from them. Maybe a
>> different gas or spark plug? There are more details
>> on that page as to the gas I've been using, etc.
>> Robert Weeks
>> Durham NC
>> 1969 Midget