I'm still not convinced that my timing is where it could be, optimally.
To recap, I seem to be able to set either:
Condition A) Timing is set to 5 degrees, car is sluggish off line, but no
knocking or pinging. Temperatur OK.
Condition B) Timing is set to 8 degrees, car is OK off line, but pings
often above 3000 RPM in 3rd or 4th gears (light accelleration). Pinging
lessens or disappears during harder accelleration
Condition C) Timing set to 10 degrees, car is GOOD off line, pings like
crazy during acceleration in 3rd or 4th gear.
When I am in Condition A) or B) (or right now, in between the two) I get
plugs with darkish deposits around the outer ring, and whitish deposits
on the electrode. It's not these strange Champion Premium plugs either,
since I got a white bullseye / black ring with the stock, recommended
Champions as well. If I rich the mixture beyond the current setting (1/2
turn on HIFs richer than starting point) the idle becomes unmanageable,
and the pinging doesn't go away.
After an extended drive at 20 mph (we have a single-lane touring road, 8
miles long) the bullseye was brown. I kept the RPMs between 2K and 3K
the entire way.
My local expert says 1) Since it's a Kent 286 degree cam the timing won't
be book anyway, and 2) he suspects a fuel delivery problem is causing the
bullseye, and lean mixture at higher loads causes the pinging earlier
than would be expected.
I've replaced the fuel filter. The carbs were rebuilt in the last year
and have worked OK since the rebuild (no bullseye). The plugs in front
and rear cylinders behave similarly. The compression is even.
Any ideas? My next steps appear to be a fuel pump and a distributor
re-curved for this cam. The local expert, who sells the distributor,
says that won't help much. The fuel pump is apparently a real SU, but
does not shut off ever... it gets much quieter when the system is
pressurized, but you can still hear it.
Thanks!
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
"You are what you is. - Frank Zappa"
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