X heads on a 273??

The 340 x heads will work on a 273 but only with modification. The Cylinder walls will need to be fly cut from the top of block towards side to accommodate larger valves. Not sure of exact machining but 2.02 + 1.60 valves = 3.62 while the standard bore of a 273 is 3.63.(No room for error) Would think that only benefit would be in upper RPM range if you went this route & port volume would kill bottom end but sure others will chime in. Late model 318(302) heads are the cats meow for 273's IMHO.

Oldschoolcuda