Whether to Lean or Enrich

"Tom Sixkiller" wrote in message
...

" jls" wrote in message
...
Not simple. Questions abound: depending on type engine, type
induction,
whether turbocharged, field altitude, density altitude, formula gasoline
(Some people love autogas), and much more. For example if your plugs
aren't gapped correctly you're going to have a serious problem sooner or
later.

I saw an O-235's plugs recently and couldn't believe the lead deposits
and
fouling. Don't know if they were gapped properly but the spaces inside
the
plugs between the ceramic and the inside diameter of the plugs were
filled
with hard gray deposits.

http://www.avweb.com/news/columns/182155-1.html (About half way down the
page).

Excellent reading. Thanks, Tom. I agree that concentricity of valves and
seats is critical and that valve face to seat contact must be broad and
precise. There are many more factors to contend with too. Such as how
much cooling oil flows across the stems, springs, keepers, and guides in the
rocker boxes and then flows down the pushrod tubes with this heat. Such as
how much pressure air flows across the fins on the exhaust port side of the
cylinder, and is there enough fin surface area there? (O-200 Continental
cylinders have always been hot on the exhaust port side because of too
little fin area.) Are the cylinder baffles and cowling and cowling seals
doing their jobs? Sparkplugs carry away destructive heat too and so do
pistons. I am looking at a set of webbed pistons which are designed for
splash oil cooling. Are the pistons and the sparkplugs doing their part?
Is the exhaust system tuned for optimum scavenging of hot exhaust gases?

There's a repair station in Berryville, Arkansas which specializes in
Nascar-style valve jobs. In an e-mail from Seth Record* he says they
balance, port and polish, flow match, and precision fit the valves, seats
and guides for concentricity. He says their cylinders will make it to TBO.
Most don't, of course, and usually die before making 1,000 hours. I
haven't seen any of PAP's work but am eager to try some of their cylinders.
They install the guide undersized and hone, not ream, it to fit, which gives
the valve a slicker bearing. Then they grind 3-angle seats. Fascinating.
I'd love to hear from anyone with experience with these cylinders. Publish
it here in RAO.





*A couple of us are about to buy some cylinders from Seth at the moment.
The company advertises in Barnstormers and other sites as Performance
Aircraft Parts.

jls wrote:

Not simple. Questions abound: depending on type engine, type induction,
whether turbocharged, field altitude, density altitude, formula gasoline
(Some people love autogas), and much more. etc, etc, etc...............


Is there a question here?