Newbie here, so I'm lookin for some help. I recently purchased a 95 Buick Riviera with the the 3800 supercharged V6. The car ran and drove fine for about the first 100 miles or so and then I noticed a "knock" in the motor. I checked the oil and it was 4 quarts low. I am assuming that it was low when I bought the car because I put the oil in and I have not used any since. However the "knock" did not go away! In fact at idle it is not even noticeable, but at Rev it is pretty good. I was told by a mechanics shop that the Rod bearings are most likely the cause. If this is the case, my question is can I replace the bottom end and be okay, or do I basically have no choice but to do what the shop says and look at a full engine replacement. How much should I expect this to cost me if I use a salvage motor. And further more, is the engine swap something that I could do on a weekend , or is this going to be a real expensive, labor intensive job. As this is my only car, I would REALLY appreciate any comments. Thanks so much...God Bless.