Well, if you want 400+ hp from your 273 you will need 225 cfm at minimum and small block mopar heads won’t get there without a 2.02 valve. And it’s .140” difference. Or 7% difference in size and actually circumferentially it’s more like 14% which which will cost you 30cfm. Notching the bore works, it’s actually a poor practice, if you piston is down in the bore. Also on a wedge head the notch isn’t the same as a canted valve motor where the valve is moving away from the bore. Also the head gaskets are 4.100. A 400+ hp 273 needs to be a perfect specimen and putting bandaides on it will come up short on power. Like I said before I would like to prove my theory. However, I have been around the block a few times with the small Chrysler and I do my own head Porting and set up as well as my own engine building. This is a great discussion because it inspires us.
