The powerband is fix so larger engine the more potential power between 2500-6500 why they do per cubic it's competition of who build the most efficient engine basically lbs-ft per cid across 2500-6500 rpm don't think smaller is really an advantage.
They are scoring by adding horsepower plus torque and dividing by cubic inches at multiple rpm data points from 2500-6500rpm, then determining an average and multiplying it by 1000.
The "divided by cubic inches" part puts a larger engine at a disadvantage if it can't make equal hp/ci at or near 6500rpm compared to that of to a smaller one. Even if it's more powerful in raw numbers.
To elaborate on this, Let's look at data points at both ends of the scale for a moment.
At 2500 rpm That 371ci made 401ft/lb and 191hp
Giving a calculated score =1.5956
This is one rpm data point to be used for the "average power"
With a 4" stroke, that engine becomes 414ci and is 11.59% larger in displacement, so would have to make 11.59% more the torque and horsepower at a given rpm to achieve the same score.
This is achievable at 2500rpm.
A similarly build 414ci could probably make be made to output 11.59% more torque and horsepower at 2500 rpm.
This would be 447.5ft/lb and 213hp.
Because at this rpm it's not a huge challenge to fill the cylinders, not at either the larger or smaller displacement.
(447ft/lb + 213hp) / 414ci = score of 1.595 points
(401ft/lb + 201hp) / 371ci = score of 1.595 points
Both achievable at 2500rpm..
But at 6500rpm the situation changes.
It's a lot more challenging to get enough airflow to fill the cylinders at this rpm.
The 371 made 403ft/lb and 498hp at 6500rpm.
So (403ft/lb + 498hp) / 371ci = score of 2.4285 points.
The 414ci version would have to make 449.7 and 555.7hp @ 6500RPM to get the same score.
(449.7ft/lb + 555.7hp) / 414ci = score of 2.4285
That's just not gonna happen through the same heads.
The 414 stroker might make more average power than the 371 from 2500-6500rpm. But not when you add the "per cubic inch" part to the equation.
I don't think it's guaranteed that 414 would done better but even if it did the point was that the more dial in the more everything is designed to work together for particular combo the better the results, that's only at 1.33 lbs-ft per cid.
In this competition, a 414 version of the same engine definitely wouldn't have been competitive, but i think it would have made more power.
even if it squeaked out 25 extra peak hp.. which would be an excellent result from a stroker crank through the same heads. It would have nosedived the power per cubic inch.
On this engine I'd be happy with 12 additional peak hp from the 414ci stroker, but the average power from 2000-5500 would be considerably more than the 371 due to the additional torque/power in the mid-range, and would make for a faster car than the 371 if geared accordingly.
My original point was the engine that gets the highest score in an engine masters competition isn't necessarily the engine that will make your car the fastest. And I stand by that.
Because horsepower per cubic inch doesn't mean anything in the real world of making things move.
With off the shelf parts each gonna favor different combo's eg.. they don't make a line heads for each displacement and various bore stroke rod ratios at different powerbands for each etc..
For sure, certain parts will favor certain combo's.
But I've not seen any scenario where increasing displacement didn't increase the average power and torque output.
Even if only a small amount.
