What drill bit or size hole is needed for a Randy Smith NVA?

Also I have an OS 20 FP (almost new), I want to convert to C/L.  I have the Brooks 6mm venturi and stock OS needle for that.  Is the 6 mm venturi good for the the 20?  I want to put it on one of my Shark 402's.  I have two of them, one with an FP 25 and one with an LA 25.  Both are too powerful or maybe longer lines.

   Do you own a pair of  dial calipers? They are a very useful tool in this hobby. Even a harbor Freight pair will suffice. It takes a bit to learn how to use them. Just measure the diameter of the spray bar, read the dial, then consult you handy dandy drill chart for the nearest size. The more you use it the better ypou get at reading one. A good set of fractional drills and number drills are handy items also, Add in a set of letter drills to fill in the gaps. The shanks of the drills can be used as pin gauges to figure out what size mystery holes are. Somewhere here on the engine section Randy has posted what the diameter is form most common used spray bars also.
  Type at you later,
   Dan McEntee

I would suggest that you could buy a better quality used pair of calipers at a hockshop for about the same price (except probably for Hobo Freight). When I first started working in a machine shop, I bought a pair of dial calipers and 0-1, 1-2 and 2-3" micrometers, all Mitutoyo, and still have and use them all.

What I have done several times in such a place is to look at what they have, ask to hold them, see how they function, and make them a "cash money" offer for the bunch. Got a Mitutoyo depth micrometer the same way. I've used this stuff for 45+ years. Most of my dial indicators were bought new, and all these tools used to get calibrated either monthly or frequently. Good stuff lasts and holds value. 

One of my prized posessions is a drill index with number, fractional and letter sizes. Well, that and a PA .51... Steve

PS: I like a .161" drill for 4mm/.156" spraybars like ST, K&B, Randy Aero, etc. That's a #20, BUT that's also for my own Delrin venturi/restrictor inserts, because plastic always drills under actual drill size.