Well so, I am aware that changing the shape of the combustion chamber in an IC engine will change the ratio of horse power to torque.
Thinking this over in my head, it seems like the way you do this is a shorter and wider cylinder for more HP and a longer and thinner chamber for more torque.
Is this correct?
My assumption is that with a thinner chamber, there’s more pressure against any square inch of the piston, but it also takes more energy to keep such a long movement. With a wider chamber, things don’t have to move as far but you also don’t have as much force, so you can maintain a cycle, but you can’t easily add more to it.
Again, is this correct?
How else does the torque and HP get modified in the transmission at a physical level, if there is any?
It’s not quite so simple - I’m not sure there is a direct answer. Generally speaking, wider and shallower combustion chambers are seen in engines which are designed to operate at higher speeds, and which may generate more peak horsepower than an engine with the same volume of combustion chamber and a smaller diameter. Remember too that the combustion chamber (and cylinder) geometry also impacts things like crank throw length, connecting rod length, etc. There is a fantastic article done by Hot Rod magazine in the 1980’s (which I have a scan of, somewhere - if I can find it, I’ll put it on my server) which explains some things about this very well and at a non-Engineering degree needed level.
Found it - here is a link to the article. It might answer some of your questions. http://www.coalgoddess.net/files/HP_and_Torque.tif
Oversquare engines (bore width is greater than stroke length), ten to rev better and produce more horsepower than a similarly setup engine of the same internal size; the latter producing more torque and lower redline.
Take a gas 3.0 litre V6 DOHC engine with basic fuel injection, and four valves per cylinder. If you take the 3 litres and configure it so that it is oversquare (cylinder bore is wider than the piston stroke), it will give up some torque versus one set up with the stroke long compared to the cylinder bore size.
The oversquare engine would give up a little torque for HP and revs and the power band would be higher.
The undersquare engine would produce more torque, give up a few ponies and have a lower power band.
When gearing these engines, the first engine would be mated to a gearbox with gears that are shorter (numerically higher) than the gears you’d set up for the second, torquier engine (which would get longer gears (numerically lower).