340 Heads on a 273 Block

The 340 heads WILL work on a 273 with some careful modification. The Cylinder walls will need to be flycut about 1/4" deep from the top of the block and a max of .070 toward the side approximately 1-3/4" wide to clear 2.02 intake valves. I can send you a sketch of what I did if you are interested. As mentioned in previous replies, unless you have a specific reason for 340 heads, the smaller heads with a good cam selection will yield better general performance. The 340 heads will make a 273 provide decent power in ONLY high RPM. They will work, but are only recommended if you are aware of what results the additional volume, port size, and valve diameter yield on the small cylinder volume.