doesnt the rod go through the block becuase the engine isnt oiled enough to deal with the low down torque, though? some people have only cracked a piston, and all the oil evacuates. i thought pistons crack because of metal on metal contact. therefore signaling that in the end, it really is about the oil anyway?
That is not correct. Firstly, pistons most-often crack because of detonation. Another reason they can crack is hydrolock or some sort of debris or contamination entering the combustion chamber. The instance you're referring to (no oil lubricating the cylinder) will cause the piston and rings to adhere to the cylinder wall first.
Then, depending on within which part of the combustion cycle this takes place, the centrifugal force of the crankshaft will either shear the piston pin or rip a rod cap (trying to pull the piston down), or bend/break a rod or punch the rod through the center of the piston (trying to push the piston upward).
A connecting rod can bend, break, or leave the engine block because of numerous things. One of them being low or no oil. However, unless you completely blow a main seal (common in older, big V8's because of poor main seal design; highly uncommon for modern engines), or forget to put your filter or drain plug back in the likelihood of an all-out oil evacuation is slim-to-none. There is nowhere for the oil to go in the self-contained system.
A sudden spike in applied torque without an ability to deliver the torque can cause driveline and engine components (like connecting rods) to bend or break as well. This is further amplified by larger displacement per cylinder engines and engines with very long strokes. The piston, pin, and rod are all generally larger and heavier because they have to displace more cylinder volume. The heavier those rotating components are, the more adversely they are affected by forces such as applied torque. The MZR DISI 2.3L turbo is a relatively large displacement per cylinder engine.
For instance, we'll assume just for sake of an example that it takes 100 Newtons to move the rotating mass for a 1.6L 4-cylinder. You can also assume that you can divide the required force by four so that during operation it takes 25 Newtons per cylinder to keep the engine rotating. Now, we'll say the diameter of said 1.6L piston is 6 inches. That makes the surface area of the piston 28.26 square inches. We can associate the weight per square inch at 10 grams/inch^2; which is 282.6 grams.
Moving on to a 2.3L 4-cylinder, you can say that it takes 160 Newtons to move the rotating mass. Divide that by four and you've got the 40 Newtons it takes to rotate the mass for each cylinder. Assuming a diameter of 8 inches per cylinder you end up with 50.27 square inches; with a weight of 502.7 grams.
As you can see, by increasing the displacement by 44% without distributing the displacement over additional cylinders, we nearly doubled the weight of the rotating mass (+78%). That is why these engines are known for bending and eventually breaking rods. That is also why they don't turn high revs like a Honda engine. Additionally that is the reason companies like Ferarri will make a V8 out of a 3.6L, a V10 out of a 5L, and a V12 out of a 5.75L and 6L.
Sorry for the long-winded post, but I needed to illustrate my point to the fullest.
