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Classic/Antique Car Repair/Carburetor adjustment


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

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.

Classic/Antique Car Repair

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Brad Sears


All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.


Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

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