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    The myth is that American V-8 motors are fun, patriotic, valuable, but inefficient and obsolete. They appear to produce much less horsepower per inch than an equivalent foreign (Japanese, German, Italian, etc.) motor, and are therefore technically backward, retrograde and inferior.

    This is not true. Horsepower per cubic inch absolutely cannot be “scaled” up or down; cylinders of different sizes and proportions behave quite differently. Larger cylinders are (generally) more efficient as to ring seal (this is physics, not quality control), and also thermal efficiency (surface to volume ratio). However, due to mechanical stress limits, they are only more efficient than smaller cylinders until they reach their piston acceleration limit (125,000 f/s/s with 1mm rings), at which point the higher potential speed of the smaller cylinder begins to have the advantage.
    A fair evaluation cannot be made solely on the basis of displacement (3000cc, for example, regardless of motor type). Dr. F. W. Lanchester, one of the earliest true geniuses of the internal combustion engine, analyzed this problem over 90 years ago, and correctly decided that comparing motors on the basis of size only gave an unfair advantage to motors with more cylinders, and favored those with larger bores and shorter strokes. He devised a formula to allow motors with different numbers of cylinders, and different proportions to compete on a fair and equal basis, with the superior product to be determined by the execution of its individual design & construction, regardless of bore and stroke. His original formula needed only slight modification to be accurate today:

HP = B^1.65 × S^.5 × N × C

    In plain English, the horsepower of a motor is equal to the Bore taken to the 1.65 power, times the Stroke taken to the .5 power, times the Number of cylinders, times a Constant representing the quality of material available, type of fuel, barometric pressure, temperature, etc. I've arbitrarily chosen to value “C” at 4 for a race motor, and 60% of that, or 2.4 for a street motor, to return a realistic number. For those of you who've forgotten their math, I've used superscript to indicate powers: “B²” is “B squared”, or multiplied by itself; “B^.5” is “square root of B”. Today's pocket calculators make easy work of this.

    Watch what happens to a 340 as the stroke is increased, using the same bore size:

    Here's a 400 B motor used as the basis:

    The following table is a series of hypothetical motors of the same displacement: 122” or 2000cc (2 litres). All are built with the proportion of bore to stroke fixed at 4-3 (such as 4.00” + bore 3.00” stroke = 302”), to remove this as a variable. The number of cylinders is the important variable. Note the huge difference in maximum power for V-12 engines.

    The following table is a series of hypthetical motors with varying numbers of cylinders, built using the same piston size (4.25”), with the stroke varied to achieve the same engine size: 454”.

    Notice that the stroke increase has very little effect on maximum power; this strongly favors motors with short strokes. The V-12's power is the result of physics, not better quality, as the formula shows!!