The formula is as follows: ci x 2 - 15% or ci x 2 x .85
4.125" Bore: 302 x 2 = 604____604 x .85 = 513.4cfm
4.155" Bore: 306 x 2 = 612____612 x .85 = 520.0cfm
Unless this guy has a huge cam, 600 is too big for a 302.
A stock 302 reguires 513.4cfm___If it's bored .040 over, it is a 306.
Common dude. The first post you have is this old ? And your telling people they don't know what they are talking about when you used a generic calculator that may get you close on a STOCK motor. PS, a .040 over motor is closer to a 308. .030 is a 306