My engine (73' F) was knocking so I narrowed it down to the crank shaft. I dropped the oil pan and found the #6 bearing to be loose. Sure enough the bearing was all jacked up. It wasn't to bad. But the shaft has some slight grooves in it from the rubbing. Can I just replace the bearing or do I have to get the shaft machined smooth? By the way oil pressure is good and oil level is good. If I can just replace the bearing can I do it with the engine installed?