Yes, if you overfill the carbs, it will spill over inside the domes when you put the piston plunger back in. That's totally normal and I'm assuming that's where the oil is coming from. It's seeping out of the carbs around the nozzle and eventually ending up on the mixture adjustment nuts.

The only thing I'm wondering about is... How long ago did you overfill the carbs? Was it yesterday and the knobs are oily, or was it five hundred miles ago and you've been driving it for six months and the knobs are oily?

hello, Captain Obvious and yes, I do fill the carbs and take it for a ride. I do check it before the next time out as it could be a month later and find oil on the mixture nut. I also thought the dome was sealed so that if over filling would be burned it off by the engine. I learned something about filling to the correct level only. 

Why do you need to continue adding oil?

I added oil because I thought I had a leak. never thought the over fill would come out the bottom.

17 hours ago, kully 560 said:

I do fill the carbs and take it for a ride.

Gotcha. So you probably don't have to do that every time you take the car out. Doesn't really cause a big problem, but as you found out, some of that extra oil will end up running out the bottom of the carbs. 

Enjoy the drive!!   

 I never check the oil level, but only when we get into the hot summer with humidity, I rebalance the carbs and notice the oil on the mixture screw. this car likes cold weather and really runs great. the summer with the hot temps and humidity I will get just a little rough idle like most carb cars.

also

2 hours ago, kully 560 said:

 I never check the oil level, but only when we get into the hot summer with humidity, I rebalance the carbs and notice the oil on the mixture screw. that is why I add just a little bit of oil. it is very hard to read on the black plunger dip stick, so I figure just add a little bit and it will burn off. this car likes cold weather and really runs great. the summer with the hot temps and humidity I will get just a little rough idle like most carb cars.