You probably can't see or feel anything that will confirm the knock.

Was this the rod with the bolt in question?
Either way, re check the bearing clearence on the #4 rod, and the one with the bad bolt after you replace it with a good bolt.

You may be able to check the clearence between piston and bore with a feeler gauge, use the service manual as a guide / instructions.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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