[chiphead]

Originally Posted by gtofreek

I'll say it again, that noise is not piston slap. The pistons are 2618 material and they require a minimum of .0045" clearance and when I measured them they are at .0047" after honing it. It's not piston slap. Doesn't even sound like piston slap. Anyone that's heard piston slap would know that.

Confirmation of piston material is helpful. My motor made a dull double knock noise at TDC and BDC, especially when engine wasn't warmed up. Since (most? all?) 8 cylinders were doing it, it had a rhythmic double rap that I got used to. I just didn't hammer on it before it warmed up. When water temps were up, the noise would be hard to hear, kinda like Sirrotica said.

I'm not saying this is piston slap for sure. One of those videos Joe posted had a double knock sound on the driver's side that sure mimics what my motor would do, just louder.

I can't imagine what else could make this noise and not come apart. Sure it sounds like it's coming from the rear of the engine near the oil pump drive. There's not much there unless the driveshaft is smacking the block d-shaft loop hard enough to make that much noise???