what is the plastic knob over the carb sync nipple called?

[a1steaksauce]

I don't know exactly how to describe it, but it is the thing that closes the carb sync vacuum nipples.
It is the thing you have to take off in order to put the hoses into the intake manifold in order to carb sync.
Previous owner must have lost it so I bought a new intake manifold set but they came without the knob to cover it.
could i just tape it up?

 

[sandmanred]

One is usually used to activate the petcock by vacuum hose connection to the petcock. The other is just capped. I cap both of mine as I have a manual petcock. Most auto parts stores sell vacuum caps. You could try tape for temporary fix but it needs to be a tight seal.