Carbon build up - blocked hole on engine head

[snicker]

When putting on a new intake I noticed that one of the holes on the engine head was completely plugged up with carbon. I believe it to be a cooling vent. I've opened it up but am curious about what problems were caused by that carbon build up. Thoughts? It is a 318 on a 69 Charger

Here is a picture. It was the hole directly under the horseshoe shaped opening:

[GreenMachine]

 That's for the heat crossover, it keeps your carb from icing up in cold temperatures and higher humidity, I think oil gets in somehow with stock intake manifolds and crystalizes.

[terrible one]

Hell, you should have left it blocked. Most do anyways. Every little bit of coolness helps.