On Tue, 17 Oct 1995, Will Zehring wrote:
> After a weekend of highway driving and a few miles of surface streets, into
> the garage and engine off:
> plugs 1 and 2 have a medium brown appearance on the electrode and a
> dry black color on the threaded ring around the electrode (fwiw: #2 is
> slightly darker brown than #1).
> plugs 3 and 4 have a dirty white appearance on the electrode and a
> dry black color on the threaded ring around the electrode.
>
> I haven't check gaps since mid August, when they were fine.
>
> My interpretation: the rear carb is lean and the forward carb is perfect.
> The dry black color suggests that my oil 'consumption' is attributable to
> the poor seal at the rear main in this early 3-main engine, and not to
> excessive burn.
>
I'd agree 100% with the following addition: If there is actually a dry
black deposit on the outer ring (as opposted to a thin layer of soot or
just black color) you may be looking at a different mixture at speed than
at idle. The outer black ring is deposited at idle but not burned off at
speed.
I had a more extreme case where the insulator was black and the electrode
was white, causing a bullseye effect. Try looking at the pluges after
idle to see what the deal is...
Excessive oil running through the combustion chamber will cause cruddy
buildup unless you have extremely "hot" range plugs.
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
Home Page: http://www.widomaker.com/~trindle
"Lowery's Law:
If it jams - force it.
If it breaks, it needed replacing anyway."
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