Just pulled engine out of wife's 84 190E 2.4 8V. Chain tensioner plastic cover and chain rail had broken and fallen into oil pan. Engine was running before I pulled it with 145 to 155 lbs. of compression per cylinder. There was metal in the oil from the chain rubbing against the bear tensioner. Do you think I can get by with just replacing the timing chain, tensioner, rails ect,,. or will I need to rebuild the motor? Also I am a bit confused, when I pulled off the lower crank gear I found a small round piece of metal in the key way that looked like it was sheared from the crank.Would this of been the key that holds the crank gear. How do I go About replacing it?