By the way, I was really starting to wonder if some kid was shooting at me, so I measured this ball. .187, not .177 like a BB. Close, though...
Still on the wheel dollies. It is a major hassle to get it on and off them. And more of a hassle to park the mav in such a way that Anna can still get her mustang in the garage beside it. Tomorrow's weather should be nice, so I will take it for a spin. I need to heat it up a bit so I can retorque the head bolts... Today we are getting the same weather that spawned those tornadoes last week.
There is a ball in the manual choke linkage. It rolls into two different holes in a plate, one when the choke is fully open and one when fully closed. You can sort of hear it when you move the choke arm by hand, it makes a slight "clicking or snaping" sound when it hits the holes. I don't know if yours is the manual choke, but it is a larger ball like you described.
My bet is that it is the power valve anti-backfire valve check ball. If it is, the first time the carb suffers a backfire through the carb your power valve will start leaking. when you replace the power valve you can install the check ball and it won't happen again.
I saw that anti-back fire kit in JEGS, it has a ball, spring, and a screw-in plug that you need to drill out and tap in to the throttle plate. I am thinking that is where it went, but I did not see the spring or plug, or even a tapped hole. Wonder if a previous owner thought he could just drop a ball in the hole and have anti-backfire set up without the spring and plug? That is the only plausible explanation I have seen for this leftover ball, and jives with vicinity with where the ball was found. So, does that kit work well? I might go ahead and set it up. It is only $15, about the price of 3 power valves...