500 cfm might run 'er well... but .. if a little is good, then more is better, least that's the way I'wuz figure'n.. So I just went aheeed and put 2 of them ther puppies on my 318 just to be sure she didn't run a tad short on my 318.... and bumped 'em up to 600's apiece..... Jeeest to make shore ...