Richard Alexander wrote:
>I pulled the plugs on '58 3A after about 1500 miles of driving. Plugs from
>1, 2 and 3 were coated with a fine bladk soot over entire insulator and
>electrodes. ...I reset the valve lash on all 8 valves, none was
>way off but I brought them all to 0.010". ...Not a daily driver but
>out 2-3 times monthly in the summer. Seems to me it can't be mixture because
>1 and 2 getting fuel from same carburator but have very different plug
>appearance.
>
>
If the black soot is easy to dust off, sounds like carbon fouling. Top
two causes would be a too-rich fuel mixture or sustained low-speed
operation. If your ocassional driving is generally at lower speeds
around town, then fine black soot might be considered 'normal' even for
a well tuned car. When I commuted the 30 mile roundtrip to downtown
Denver in my TR4 from 2000 to 2003, I had to clean the plugs fairly
regularly because almost all my driving was low-speed. After a year I
switched from Champions to NGKs, and I found the latter held up better
in stop-and-go driving.
I wouldn't rule out mixture either. It should be easy to check, and it's
definitely worthwhile to retune your SU's with the change of season
anyway. But if you don't have any misfiring, I don't think you're facing
a major problem. If you haven't seen this one, here is a web page that
shows a bunch more plug conditions (29) than the usual charts (11 in my
Haynes manual for the old Volvo).
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
Steven Newell
Littleton, CO USA
'62 TR4 x 2
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