I know that rod knock is typically attributed to worn bearings where the rods connect to the crankshaft. However, is it possible to get some rod knock from the smaller brass bushings that connect the rods to the wrist pins? I recently did a budget rebuild of a 22r and I have a light knocking sound at certain RPM. It's not very severe at all and I have almost 10,000 miles on the motor and it hasn't gotten any worse yet. It's kind of a light pattering/slapping/knocking sound. At certain RPM its totally gone. I know it's not the valves. The only thing I can think of is perhaps those brass bushings as I reused the same rods and did not replace the bushings. Anyone else experienced this or have any thoughts on whether this may be the cause of my noise?

 

I had a car that had a crack in the piston at the wrist pin. It was a constant knock and there was oil consumption but it ran ok. If you pull plugwires individually you can probably isolate it to a cylinder.

 

Interesting. That's a good tip. I suppose it will run well enough on 3 cylinders to do this check? I could turn the idle up higher before unplugging to be sure it doesn't die.

Yeah fortunately this knock I have is mild enough that it's really not too distracting or obnoxious. But it's there enough that you know something isn't quite right.

 

The pulling plug wires method is a pretty standard way of locating rod knocks also.