Gerald M Van Vlack wrote:
>At any rate if anyone among us can define how to determine if I have too
>much carbon build up in my engine without a tear down I'll buy them a beer
>at the next TRF Summer Party after the Saturday night downtown show.
>
>
>
Actually, Jerry, there's a fairly simple way to determine precisely
that. Most cars will exhibit some driveability problems, including
those you mentioned. But, to determine if accumulated deposits (of all
types) are the cause, the oscilloscope will tell a great deal.
Accumulated deposits interfere with the spark plug's ability to
fire--effectively, the electrodes become electrically insulated and the
resistance increases--that simply adds to the voltage required to
produce an arc. With an oscilloscope connected, spraying small amounts
of water a little at a time into the intake will steam-clean the
chamber, including the plug electrodes. If they're heavy with deposits,
the difference in the amount of voltage required to fire the plug before
and after water treatment will be noticeable--I've done this many times,
and the differences can be substantial--often 12-15kV and occasionally more.
A second way is to track valve lash over time. Typically, valves lose
clearance with wear, partly because of valve seat pounding (which
eventually deforms both valve and seat) and partly due to valve face and
valve seat ablation. If clearances begin to increase, particularly on
the intakes, that's a strong sign of carbon accumulation. Over time,
that accumulation becomes severe enough to cause irregular compression
readings.
Cleaning the chambers doesn't hurt anything, if done a little at a time
(the process can be sped up somewhat by also spraying small amounts of
carburetor cleaner into the intake, but these days, for most cars, one
has to be sure that the cleaner is compatible with catalytic converters).
Cheers.
--
Michael D. Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking distance....
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