Ld340 intake holes

http://s117.photobucket.com/user/djmdragracing/media/ld340.jpg.html

This picture is representative and I borrowed it from a google search. This is not my photo. I am referring to the hole on either side of the intake below the carb base in the middle. Disregard the arrow in the picture. That is not the hole.

What is the purpose of these holes? They are quite noisey and sound like exhaust coming through. Is it ok to block them?

This same intake is installed on my 273 commando. I bought the correct manifold for it but for now I would still like to know what these holes are for and if they can be blocked. I searched fruitlessly for hours. I'm sure it's simple. Thank you for the help.