I am trying to nurse along a old engine that was apparently not taken care of by the original owner. It is the infamous Dodge 2.7 liter that is known for sludge build up and yes the main timing chain is starting to rattle. I want to try to clean it out using Seafoam. Has anyone done this? How long or how many miles do you run the engine with the seafoam in it before you drain it and put fresh oil in? Any pointers are welcome.