I agree with the finger nail method for a better check than visual. If you feel the grooves it wont polish out for good results. you want about 1-3 thou between the bearing and crank. anymore than that it will start to knock. A typical human hair is 3 thou so if you "polish the grooves out you will be undersized. Not good. A shop can turn it down 10 under and then you can get 10 over bearings and be fine. hand polishing will only take abot 1/2 thou out and that will still leave the grooves if you can feel them. Dont build a compromized motor. Have it turned down should be relatively cheap Less than 100$ I would think. Thanks

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83 300D 227,xxx miles, sold
86 300 SDL 130,000 miles, sold