Several thoughts:
(1) With all due respect, you have probably either misread the number, or the fickle typing fingers typed the incorrect number. Probably should be 964s rather than 864s.
(2) The better rebuilding kits DO contain the jet.
(3) If I guessed correctly on the 964s, it is an aftermarket carb, so the only specification sheets are contained in the Carter Master Sales & Service manual, and yes, they are in this manual.
(4) 90 percent of the time, rich running is caused by defective ignition. Would suggest checking this second, after you check the compression (5 percent).
(5) If the compression and ignition are both good, you have not installed a powerful electric fuel pump (the YF likes about 3~4 psi)) and you have not installed a pertronix conversion in the distributor without also installing an alternator; then a good carburetor rebuild is in order.
(6) If the carburetor is built to stock specifications, and you are using ethanol fuel, you are far more likely to be lean than rich; HOWEVER, if you are running rich, then Wrenchbender's comment about the rod is spot on. With Carter's sophisticated metering rod technology, simply changing a jet (unless it is a very MINOR change) will guarantee that the metering will be off at at least one value of vacuum. The metering rod technology allows for the calibrations to be set at multiple values of vacuum; as the effective metering area is the area of the jet less the area OF THE PORTION OF THE ROD CURRENTLY IN THE JET. But this technology also means that a recalibration should be done with a different rod. And if the diaphragm is bad, fuel will syphon through the diaphragm and cause a rich condition.
Suggestion: do some more testing. If you do have a 964s carb, it is one of the finest (opinion) carbs you can put on that engine. If after testing, you are sure the issue is the carb; and need either help or parts, call me (573) 392-7378 (9-4 Mon-Tues central time).
And one final suggestion: if you have installed a pertronix conversion, I would suggest replacing with the original points/condensor FOR TESTING just to see what happens. The two most common "carburetor" issues we see are pertronix conversions and ethanol fuel. I won't try to talk you out of using it, but it certainly can be a problem!
One late thought: again, assuming I guessed correctly on the 964s,the orifice for the fuel valve should be 0.081 inch. Most of the cheap kits have an orifice of 0.101 (for the Ford 300 CID six). Too large a fuel orifice will cause the fuel level in the bowl to be too high, thus causing a rich condition; but this is not the fault of the carburetor.
Jon.
