Sealing problems and piston ring damage
skewing of pistons
Bending or twisting of the connecting rod often occurs after engine damage. That can result in skewing of the piston. You can find out in this article what the consequences of skewing of a piston are on the engine and what damage may result here.
Engine damage frequently also causes bending/twisting of the connecting rods. If the big and small connecting rod eyes are not checked for parallelism during reconditioning or if the connecting rod is not aligned straight, skewing occurs on the piston in the cylinder during subsequent engine operation.
The piston rings will not run in a true circle in the cylinder, but will trace an elliptical pattern. This causes severe sealing problems.
The piston rings will make contact at the bottom on one side and at the top on the other side of the cylinder. If the ring is still able to turn in the ring groove, it will be crowned in just a short time. This crowning significantly exceeds any level of crowning desired as a result of the design, so that the lubricating film becomes much thicker and makes good oil scraping performance impossible.
As the piston is skewed, a pumping force will also be applied to the piston rings resulting in the increased ingress of oil into the combustion chamber.
Frequently, the skewing also means that the piston rings are unable to turn and deflect into an elliptical form. This causes uneven radial wear, which often results in the piston rings breaking.