I took college physics. I learned that power is unit work per unit time, which can be expressed as newton-meters per second. Torque is a cross-product quantifying rotational force accounting for a lever arm, which is expressed as newton-meters. I know that the distance in the measurement of torque is perpendicular to the direction of rotational motion whereas the distance in measuring power is parallel to the direction of motion, so these are not the same “meters” at all. But both of these involve a measure of force – more force means more power and it means more torque. However, when it comes to car engines, two engines can have the same horsepower but very different torque. Why do HP and torque not increase in lock-step? Is this just a matter of available gear ratios in the transmission? Or is there a way to build an engine deliberately to make torque vs. Deliberately to make horsepower independent of the transmission? Thanks!
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The 1955-1990’s Chevrolet V8 family had a block where a wide variety of components could be swapped around for various combinations of bore and stroke. Of course the bore is cast into the block, and the stroke is the configuration that can be changed easily by the home builder.
The 350 cubic inch displacement version was probably the most common (roughly 4-inch bore and 3.5-inch stroke). For this example, the blocks could be had in a 400-cubic in displacement.
If you used a 400 block and swapped-in a 350 crank, you had a big-bore/short stroke engine at 377 ci, and the large valves that were allowed because of the largebore created an engine that could easily rev to 7,000 RPM’s and make a high peak horsepower. However, at low RPM’s it had less crankshaft torque than the 350 due to poor cylinder filling.
Reversing it, you could take a 350 block and swap-in a 400 crank, creating a small bore/long-stroke 383. Peak horsepower was down compared to the 350, but it had more torque across the entire RPM range, with a very noticeable improvement in low-RPM torque…
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