mystery knock

[whitemonster70]

My '70 recently developed a rather scary knock. At first I thought it was the bad gas I put in.. but its not. Its not rod knock, as it disapears above 2500 RPM or with any load. It is heavy enough to feel though the floor. Another thing is that it only occurs when the engine is warmed up at 190. I have good oil pressure, and no overheating problems. Any ideas? The engine is a 351 Modified

Thanks

 

[Bully Bob]

Hmmmm,

Maybe piston slap...?

Have you tried removing plug-wires, one at a time, to isolate which cylinder, if in fact it's cylinder related.

"Piston slap" is a piston that's tapered at the skirt enough to flop against the cyl. wall.

Not fatal but annoying.

 

[charmon]

Hmmmm,

Maybe piston slap...?

Have you tried removing plug-wires, one at a time, to isolate which cylinder, if in fact it's cylinder related.

"Piston slap" is a piston that's tapered at the skirt enough to flop against the cyl. wall.

Not fatal but annoying.

That sounds like something I have going on myself, What did you come up with? Chris