Classic/Antique Car Repair: Carburetor adjustment

Question
QUESTION: I have a high performance flathead V8 ford 39 ford with two FORD carburetors, both carbs.have .050 jets and I recently rebuilt them ,float is set to manufacture spec. Needle adjustments are 1 1/2 turn out on both carbs. The choke linkage is set to middle position ( of the three position )  plugs black, burning rich. How would I set the carb. As a base point to have the carbs run less rich. Is actually turning in the needle jets one carb at a time until the motor starts to stall then back seat the needle until motor runs smoothly as a starting point.

ANSWER: On a high performance engine spark plug color is only a valid indicator of mixture when the engine is being run at the speeds higher than the cut in RPM of the cam shaft. Most modified engines run rick at or near idle conditions. When I was active in racing sports cars we would put frech plug in the car and make a half a dozen laps at racing speeds then pull the car into the pits, remove the plugs and read the color and condition. So the answer to your question depends on the grind that you have on the cam shaft, 3/4 quarter, full race. or what ever. The carb adjusting method that you describe is the one that I use.

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QUESTION: Running 3/4 race cam, finned Offerhauser aluminum heads , headers, aluminum intake manifold, converted to a pointless ignition years ago went from 6 volt positive ground to 12 volt negative using a modern alternator. The car starts flawlessly for many years since I had it converted to pointless ignition. I'm not going to tinker with it that much, just trying to get the richness down a little if possible.

Thank you

Answer
My own flat head. a 1941, runs the same set up as your car. I have done all the dance steps with this car and in order for it to run its best it runs slightly rich. Since I don't drive it hard I found a set of Champion H11 plugs which is one step hotter than the H10 s. I have run it several years that way.