Don't read if you're close minded

Most of us aren't building high effort, highly competitive racing engines, and most of us aren't even close to running port sizes with those cross sections and volumes. I've never heard anyone say the X head was too much for a 340 or that the 1.88 J head was an improvement to a 340 or porting a 340 head turned it into a slug. A 340 has about a 2.1 cid to port volume same a 273, 318 would need a 151 cc port, 360 171 cc, 408 195 cc to be in similar ratio as a stock 273/340.