Lets say rpm limit is 7k and engine size is 555.....There are a number of combinations to get near the cube limit, but which would be quicker? A smaller bore and big stroke, or a big bore small stroke?

My thinking is that steep rod angles hurt power. I'd llean towards a bore that's equal to or larger than the stroke. but that's only my thought, I'm not an engine builder.

A lot of other factors go into which would be "quicker", but for a given engine family, go with the biggest bore which is practical, then adjust stroke to get the cubes desired.

Bigger bores mean more reciprocating weight and more drag.

I imagine the proper answer is a nice blend of the two.

I'm thinking the type of motor, N/A or what type power adder, will have something to do which works better.
Don't most of the faster all out Pro Stock N/A motors have a 4.625 size bore with less than 4.0 inch stroke to make 500 C.I.. On your deal I would look at 4.5+ on the bore and around 4.375 stroke to get close to 555 C.I. Adjust as needed
My next all out N/A motor will start as a 4.500 bore Koleno block with a older 4.375 stroke Bryant top fuel full counter weighted crankshaft with 2.200 rod journals with B1-MC heads and a pair of Dominator carbs

Not sure but I ended up going with 4.5 bore and a 4.35 stroke. Using 7.1 rods with 2.2 rod journals. Ends up being a tad over 553 CI.

On gasoline, the biggest bore possible makes the most power, because moving the cylinder wall away from the valve improves flow. Assuming adequate cylinder wall thickness for effective ring seal.

Wedge or Hemi ? Wedge the big bore Short stroke seems to be the go to...... Canted valve leans towards Big Bore short stroke also
.... for Hemi....... I don't think it matters as much.

Current Pro stock thinking is 4.71-4.75 bore and stroke in the 3.5, 3.55 depending on deck height rods are in the 5.95-6.10 range .Last DRCE my uncle built was a 8.70 DH , 4.71X3.55 with 6.10 C to C rods.

Stroke will make more power, most engines can only go .060 but you can stroke them 1/2 inch or more. Chevy, I know I know, 427-4.25 bore x 3.75 stroke, 454 4.25 bore x 4.00 stroke, which makes more power turning same rpm?

One of the magazines did a big bore short stroke vice versa dyno comparison some years ago. Same heads, cam and induction.

I don't recall the difference being more than a few HP.

As far as which one might be faster, I suspect if there is any difference between 2 engines that make the sameish power, it will be the engine that can accelerate itself the quickest.

Kevin

500 inch blown fuel engines are long stroke, small bore. 500 inch gasoline ProStock engines are big bore, short stroke.

Torque monster - more stroke. Peaky high RPM - big bore, big valves.

7k limit would favor a long stroke.

From my experience, you want the biggest bore, and still keep the cylinder walls thick enough they do not flex, you don't make any power if the rings don't stay sealed under power. And on the dyno testing, just keeping track of the engines I dynoed, the peak numbers may be close, but those that I did the average HP numbers were always higher on the big bore engines, and higher average numbers usually will out run higher peak numbers given the same chassis combination. The best example was to 383 small block chey's I built for mud jeeps. One was a 350 block stroked, the other was a 400 de-stroked. The 350 had some better heads, and made about 20HP more, but the 400 had better average numbers, in the mud pit, the 400 jeep smoked the 350 block.

The fuel motors really need the wall thickness. Plus the slow burning nitro doesn't mind the long stroke.

Same heads, cam and induction

That's the reason.

In the mid-level typical bracket race engine(1.5-ish hp/ci), assuming the head/induction/exhaust are identical between the two configurations(and are appropriately sized for the desired output) I would expect the power difference to be negligible, especially if there is going to be an upper rpm limit of 7K.

7000 rpm is the limiting factor IMO. Would likely flavor more stroke. But generally a bigger bore will make more power than more stroke, but when you are talking BB Mopar the bores are not very large for sure. The old saying bore makes power stroke moves where it happens.

Why would you keep everything the same? The bore and stroke needs to be considered when building the rest of the motor. You can use a bigger intake valve if you have a 4.5-in bore versus a 4.310 bore. Cam events would be different with a shorter stroke versus longer stroke, and the intake. That's the problem with some of these comparisons that the magazines and TV shows do. They don't build the motor around the one variable that they are testing.

As long as the bore doesn't restrict the size of the intake valve at the desired RPM level, it doesn't make much difference. If your combo needs more valve and it won't fit. Then it needs more bore.
Doug

So the bigger bore shows its an advantage right there.

You don’t understand, ya gotta play with what you have available. Really like to see some of these 5” bore mopar engines. Like hitting a nail, short swing, nail won’t go deep, big swing that nail going clear thru. Bigger hammer might help a little but big swing gets the job DONE. One of the 5 basic tools, a lever!