VM 26 Holes in carb body, some plugged, some not?

[tobaccorancher]

Hi, I was into my carbs today to replace my choke plungers. While I had the carbs out I took the bowls off to have a look and I see what looks like factory holes in the carb bodies. Some of them are plugged, some not.
Each of my carbs is different in this respect. I am a carb novice, so I hope that one of the gurus can tell me what is going on, hopefully not serious. Thanks! Andy

carb1 The right hole looks like it is plugged: carb1 by Andy Hoover, on Flickr
carb2 The right hole looks like it was plugged, but has either been drilled, or the plug is coming apart: carb2 by Andy Hoover, on Flickr
carb3 The left hole appears to be plugged carb3 by Andy Hoover, on Flickr
carb4 Both holes are unplugged: carb4 by Andy Hoover, on Flickr

[zed1015]

The carb bank is made up of two identical left hand body castings and two identical right hand body castings which are simply machined differently depending on their final location on the back plate and whether they are positioned on the inner cylinders or outer cylinders.
For example , carbs 1,2 and 3,4 are linked as pairs and each pair shares a common breather so only one of each pair needs to be drilled for the brass breather outlet.
The carb body with one breather hole links via a rubber cross tube to the neighbouring carb with two holes .
The second hole in the other carb leads to the brass breather outlet tube.
Carbs 1 and 3 only have one hole with 2 and 4 having two and you will see that that 2 and 4 also have the brass breather outlet.
If you have a vacuum operated fuel tap then number 3 carb will also have a brass outlet which is in the same position as the outlets on 2 and 4 but is connected by different internal drillings to the venturi bore to enable the vaccum tap to be activated once the engine is running.

[tobaccorancher]

Thanks, Zed!
Andy