250 with 'rod slap'?

[Invectivus]

I have a line on a 250 getting extracted from a mustang, apparently it has a cracked head and 'rod slap'. Can anyone give me guidance on what that is? I know what piston slap is, maybe the rod is stretched out of round and rattling in the journal?

Generally as long as the block can be bored out (if there's cylinder wall issues) and the crank journals can be smoothed, I don't really care. I have an AL head so I won't cry over the cracked head.

EXTRA CREDIT: I saw some posts that I can't find, relating to connecting rod/piston replacement options for the 250 that allowed for significantly smaller crank journals in order to increase stroke through greater than normal offset grinding. All I can find is some on offset grinding to de-stroke the engine, the opposite of where I want to go. I'll keep looking, but if anyone remembers anything that may help, I would appriciate it.

 

[Anlushac11]

When my machine shop guy looked at crank he said it had been built before but instead of getting rod journals turned the rebuilders put stock size rod bearings in it and put it back together.

As such there was too much clearance between rod journal and inside surface of rod bearings. You could see where the rod bearing was hitting rod journal surface as crank reached top dead center and started to come down but rod was still going up.

Same thing happens when crank hits bottom dead center and starts back up but rod is still traveling down.

Had to get rod journals turned .020" under to correct this.

Anyhooo thats what I thought rod slap was, when worn out rod bearings let rod slam to a stop instead of a nice tight well lubricated reciprocal motion.