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At 07:50 AM 12/13/2005, John Silberman wrote:
I was told at one time that much of the lead fouling came from
running the engine at to low percent of power, to save fuel. That
at these low power settings the engine was never really hot enough
to burn off the lead. If this is so, what power setting will burn
off the lead rather than let it accumulate in the plugs, or what cyl
head temp would correspond to it.
What's critical is the combustion temperature. Leaded fuels contain
a lead scavenging agent, ethylene dibromide, that combines with the
lead in the fuel and helps carry it out with the exhaust. This
chemistry only works at temperatures in excess of around 1000 degrees
F. Idle and low speed operation (ground ops) do not generate enough
heat. Any cruise power setting should be sufficient. Leaning helps
too by lowering the amount of lead that has to be dealt with.
Unfortunately, the Stromberg carb cannot be effectively leaned for
ground ops as the mixture control is tightly coupled with throttle
setting, but, again, in the absence of sufficient heat, the lead will
not scavenge anyhow. Use of a product called TCP can help as its
lead scavenging operates differently. Once lead deposits coalesce on
the plugs they are extremely difficult to remove by other than
mechanical means.
John Cooper
Skyport Services
PO Box 249
4996 Delaware Tnpk
Rensselaerville, NY 12147
518 797-3064
Fax 518 797-3865
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