General 318-340 questions

Get it checked to see how thick the walls are but I see no need to go more than 60 over 3.97 x 3.31 = 328 it's just a hair under 4.00 bore and 12 cid less than a 340 a 3.5% difference, on a 350-450+ hp it ain't gonna make a big difference maybe powerband moved up a 100 or 200 or so rpm's and 10-20 lbs-ft.