Overhaulin'

What is the big round thing you see on engines on classic cars?

I been to car shows and see them all the time - but not exactly sure what the function of it is? eg. http://www.classiccarauto.com/impala/articles/images/64_Impala_engine_w-ac.jpg

Public Comments

1. as many times as your mother told you to stay away from car shows//
2. That is the air cleaner. It sits on top of the carb.
3. is it the air filter? the picture wont load. haha.