Join Date: May 2009
Location: North Carolina
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To conclude my thoughts:
Short of a significant fitting issue with the upper to the base plate, I don't know how else fuel could be getting past the mixture screws. I believe on the 2 bbl there are 'transfer passages' below the throttle plate when it is closed that allow the fuel that comes past the idle mixture screws to get into the intake with closed throttle.
Brand new 6.5 power valve this morning made no apparent difference.
Elsewhere someone had said the black exhaust was due to weak ignition. Now I have a new distributor/coil/rotor, all spark plug wires have reasonable resistance readings and brand new plugs.
Any thoughts would be appreciated.