159 cube four bearing Falcon 144 with six Amal carbs and revs to 8400 rpm. That's why you'd rev an engine past the power band. Especially if the competiton was a 155 cube Flathead V8 Ford. This is the history of hydroplane Ford engines, absolute examples of why you'd over rev an engine which couldn't pass 5500 rpm in a 1960 Falcon XK 2000. Similarly, the old race 240 and even 330 cube engines based on the Ford 300 blocks. These engines were messed with in the most insane ways, with port on port carburation and injection, canted valve heads, and long rod concoctions with reject Ford V8 aftermarket parts. Suddenly little Mavericks and Altereds started doing scary stuff at US drags. Same in Australia, where little 208 cube stroker I6's used to do 12 second quarter miles in stock 100" wheel base sedans. Today, 250 cube sixes are the hot property in little Fox sized Cortinas or Fairmonts, simply because the proverbial crap is wrung out of them with high lift cams and great breathing heads.
Years of racing has proven that the engine which revs less to produce the hp wins the race. That is efficency in its truest sense. However, the capacity, rod ratio, head design and bore spacing of the engine interplay with this, so you have 6 liter alloy chevs beating Ford DOHC Romeo and Windsor engines, and Chrysler 340 and Ponitac 455's suddenly making much more power than they should, often taking out 351c's and 460's just because the designs allow better power at lower revs.
The point with our Six cylinder engines is the same as comparing low tech LS Chevy small blocks with Ford DOHC V8's. Each might yield 400 hp, but at different rpms with slightly different manners. Or perhaps comparing a modern 4-valve Toyota 4AGE with a Mini Cooper S a-series engine or older two valve per cylinder Lotus Cortina 1558 cc engine. Both might yield 126 hp, but the A-series might have to run to 8500 rpm to get that, or maybee a six DCOE carb quad cam 4 liter Lamborghini that yields 375 hp at 8000 rpm but an inferior 4-bbl 4.1 liter Falcon six might yield 375 hp at 7500 rpm.
If you cary extra rpms and capacity, then you can always make more power. Power is always PLAN.
Power is HP
P is PRESSURE
L is stroke Leverage
A is the area of the piston
N is the number of cycles the engine has
Comparing apples with apples, a 400 hp 5.4 Ford 32 valve engine might make power at 5250 rpm, with a 5900 rpm the top engine speed. For a 5.7 liter Chevy LS to do the same, it has to rev to 6000 rpm for power, with peak revs upwards of 6600 rpm. The Ford dohc is roughly 30% more powerfull in terms of specific power than an alloy chevy.
For example, the Chevy engine produces better specific fuel consumption, but not better specific power than the Ford engine. It revs 11% higher than the Ford, and takes 6% more capacity, and revs to a level 14% more just to get the same Hp figure. For every horse power, it requires more revs (N) and more capacity (A).
The key manner to finding how many revs are required to make more power are how much port on port 'carburation' an engine (how many square inches of port area at the gasket face)has, and how much specific BMEP pressure the engine can garner. You'll find that the 630 to 650 hp NASCAR 5800 cc and a TransAm 5000 or Formula 5000 engines based on the old canted valve or angled valve Detriot engines are second to none under race conditions. It may be that a Cosworth DFV might make 600 hp with less capacity but it has to rev more to make up the difference.
