I'm in agreement with zope_pope and Truckracer.

While the engine will probably run with it that close to the firewall and no hole, it certainly won't run well. There is actually a formula for figuring the necessary minimum clearance from the carb inlet to the firewall, but it basically boils down to you need at least the diameter of the carb intake i.e. a carb with a 5/8" intake would need at least a 5/8" clearance to the firewall and that's the minimum.

JMHO...