there is one more thing to keep in mind;
engines are all about getting air in. Adding the fuel to it is relatively easy, but trying to get more air into the same sized cylinders is always the hard part.
To that end it must be remembered that Air moves from a high-pressure area to a low pressure area. Engines do not suck in air. The atmosphere muscles it's way in.
The piston, falling on the intake stroke as it does,creates a low pressure in the cylinder, that the higher pressured atmosphere then tries to fill.
But the carb/intake manifold/intake valve all make it difficult, especially at idle, with the closed throttle valves. So our jobs as performance enthusiasts, is to make the airway from atmosphere to piston, as easy as possible for the atmosphere to traverse, and to try and reduce the pressure in the chamber on the intake stroke, as low as is possible, to encourage maximum air infiltration, and to try and get as many oxygen molecules stuffed into there as possible, during the "time" that the intake valve cycles from open to closed.
That "time" is principally governed by the intake duration of your camshaft. But, there are some tricks we use to try and encourage the atmosphere to come in early/stronger and pile up longer, during the allotted "time".
It's all about getting the oxygen in there.
A big cylinder to start with, is always the easiest way,lol. Once the size of the cylinder is chosen, there is only so much you can do.
It helps me, to think of the basic size of the Mopar cylinders; A 360 has ~752cc. A 340 is ~696. a 318 is about 652. A 273 has about 559cc. It's pretty easy to see that 752 cc of air would seem better than 559cc. That's a difference of 193cc or nearly 35% from small to large. That's a lot of air. Rather could be a lot of air. But it's more complicated than that.
It's complicated by the application, and by the desired useage, and the environment that the engine is gonna have to operate in, especially altitude. I mean a 5000 pound tow truck operating in the mountains would want a different engine than a 2800pound grocery getter at sealevel. Or a peppy 3400pounder at a more typical 1000 ft elevation. There is a home for every size of engine. But sometimes we try and make a too-small engine, work too hard. And sometime there really is such a thing as too big.
We can do a lot with camshafts to try and better fit the engine to the applications, but sometimes it's better to just start with the right sized engine in the first place. My yardstick for that, for a performance street application, is 10 pounds per cubic inch. So; a 340 would seem to be just right for most of us, with 1967 to 72 A-bodies, with a middle-aged driver,lol. The later fat-boy Swingers like 360s, and the earlier lightweight-As can get by with less cubes.
After the basic size is chosen, the power can be varied quite a bit from say .75 to 1.15 hp per cube, to fine-tune for the application. But for the most part, sticking to .90 to .95 is gonna make the most trouble-free engine at the most economical price, and be the most fun.
It's all about getting the air in. Trying to get 752cc of air into a cylinder of 752cc is tough enough, never mind trying to get it into a 652 cc cylinder.
_____________________
To try, IMO, is either;a rich-man's quest,a poor man's folly, or an exercise in futility. I ain't rich and my Momma didn't raise no fool; so my 3650 pound 1968 Barracuda (me in it), has....... wait for it ...... a 367 cuber.
I couldda built a 340, but then I wouldda wanted to cut out 200 pounds from the car.
I couldda built a 318, but then, my Barracuda, at 3450 now is a tad porky for a 318 at .95 hp per cube so now I would have to pump it up to say 1.13hp per cube, to match the power of the 360 at 1.0 hp per cube. But doing that, always,always, trades away low-rpm power to get the higher absolute power. So now I would have to deal with the wet-noodle bottom end; no thanks. I'm not into 3200rpm stalls and 3.91s. I actually drive my cars, some years 12,000 miles. A 318 does not fit my application. I drive a Manual-trans, and am limited to 3.55s, 3.23s preferred, so a 318 is not gonna cut it, I don't care how much power it makes; where I drive it, in the sub-3000rpm zone, a 318 just cannot process enough air for my preferences, my driving style; it's a poor match to my porky chassis.
A 340 wouldda bin a good match at 1.06hp per cube, but in my case, I wanted overkill at low rpm. So I chose a 360 at 1.0 hp per cube ....... but that quickly morphed into 1.15hp per cube when I found out just how overkill my 367 bottom-end actually was. I traded some of it away, to get the top-end rush. Yeah, it really is too-big, but it sure is fun.
I was fortunate in that, at the time I was working on this car, I was making good money.So I was able to do the things I did without compromising my lifestyle. I realize that not everyone is so blessed. So I'm here on FABO to try and help steer people into the right combo for them, the first time. But also here to share what I have learned, with the next generation. I'm 67 now, semi-retired, and running out the clock of my promised 70 years/80 if by reason of good health. " You can't take it with you" also applies to knowledge, so I share what I know to anyone who asks. If I die stoopid, having emptied my brain of knowledge, I'll be a happy happy man. I have, officially, 3 to 13 years to get it done.Time after 80, I will not be actively seeking. I get what I get.
