Today, dollar for dollar, is the 318 faster than the 340 ???

Bore size is the limiting factor to max hp potential of a given block, cause it determines max valve size and that determines max flow amount. But no one is building engines to there max potential except Maybe F1 NASCAR etc….

So rpm becomes the limiting factor, that depends on the person, most build to make peak power in the 4500-6500 rpm but a smaller group is ok with 6500 - 8000, 9000 plus.

But since 318/360/340 all take the same performance parts other than pistons for the most part, and since the bore size isn’t overly different between the 3 engines there potential is about the same, sure the 3.91 is gonna give up some flow over a 340 especially a max overbore one but how much at what level ? Is there gonna be a massive difference with a set of eddy heads or even trick flow ?
Haven’t seen anyone do flow bench comparison, but seen some 305 vs 350 bore comparisons and it was like 5 cfm on the heads they used. 318 bore is much bigger, and displacement there’s only about a 15 cid difference between a 318 bore and 360 if you got the same amount of overbore and using same stroke it’s only when you limit yourself to stock strokes cid is a bigger difference . But even with stock stroke a 360 is only 13% larger and a 318 would only need to move the powerband up 13% to make about the same maybe a little higher to makeup for bore difference but a .060” overbore 318 vs a .030” overbore 360 I would ain’t all that big of deal for most builds.