I have been offered an old 350, but I am told it has a rod knock and of course has to be rebuilt. What exactly causes rod knock? Bad bearings? Bent rod hitting the cylinder walls?
I may have it machined to make a 383 but would a rod knock cause damage to an engine to make it unsuitable for a performance engine?

 

As far as I know a rod knock is usually caused by a bad rod bearing. Usually the bearing will go bad and chew up the crank journal that it's on. Sometimes the particles can get around and eat up an entire engine. Just don't count on reusing the crank or the rod(s). Also make sure the block is checked thoroughly before being machined.

 

about every time some one says an engine has rod knock it doesn't. people like to assume the worse and not truely ID the noise. at any rate i wouldn't let it scare me away from the engine.

 

piston slap maybe? if so its bad rings and if it is really bad the cylinders would be ipretty bad shape to