How does cid make power?
Yes obviously if we take things to the limit max piston speed same level of bottom end parts a 273 can't turn enough to make more than even a 318 since both would have the same rpm capability. Ultimately piston size limiting factor so with stock blocks 400/440 have max bore capability, If you bored a 400/440 to 4.375" and no matter what crank you use 3.38" 3.75" 3.915" 4.15" 4.25" etc.. Taking it to max piston speed they all dispace the same amount of air, same theoretical capability of hp, so my question that I was trying to get at and finally figured out why can't the 3.38 spin up to make same hp as the 4.25, what's hindering it ?
OK, so we agree that in 'never never land' where we're not constrained by the realities of availability and OEM-designed engine architecture, bigger is always better.
So if we approach the question with some measure of reality the reality is that RPM is HARD and EXPENSIVE and all the things which let a 3.38 'spin up' will let a 4.25 spin up too. The only thing 'harder' about the bigger motor is getting bigger heads, and only because these aren't chevvies and so we can't just go buy a 400cfm head off-the-shelf from Summit tomorrow...
Getting an engine to 7k is relatively easy. 8k takes work. 9k+ is a whole other world, and 10k is not for the casual tinkerer. That's why the 273 "can't" be spun up to make the same hp, because cubic inches no longer cost cubic dollars - but RPM does! If you've got the time and budget to make that 273 rev that high, doing the same to a 408 is kinderspiel. There is nothing intrinsic about stroke or piston size which limits RPM. With strength-optimized pistons, pro-stock cars run 4.7"+ pistons at well over 10k! So why do strokers tend to disappoint? "it's the heads, stupid"
Not only that, but the development has already been done for ~4" stroke motors to run that high, and the parts can be had, and a 273 bore is too small for those valves/heads. So physically you're time and money ahead going for greater displacement in that regard - imagine that, smaller somehow costing more. 900hp 410's are not mythical, just atypical - mostly because people are cheap and would rather not source and fabricate a w2/5/8/9 top end.
Here's the thing from an engineering perspective. The benefit to smaller displacement is lower weight. If I wanted to get high revving HP from a smaller displacement, I push the bores closer together. If I can't push the bores closer together I'll shrink the stroke to get the block deck lower to shorten the intake tract. Can't do that with a stock block - at least not to an appreciable degree, and the parts to do so will become custom and thus $$$$ in a hurry. If I'm a dedicated race team, I don't care - but if I'm a hot rodder, I do! That's why it's common wisdom - because commoners aren't race team members.
I keep this link bookmarked because there's a post in there which shows the math to develop a race engine. Lots of the smaller details and constraints get brought up and you can imagine the impact when each variable is altered. Give it a read, you may find it illuminating.
