[glhs#116]

So.. I've been fooled before by a terrible sound that sounded a lot like rod knock. it was generally my torque converter bolts loosening up. But this doesn't seem to be that.

1971 455 HO with Edelbrock 87cc CNC heads. Crower 61919 "041" cam. Harland Sharp roller rockers.

So, the start of this whole thing was putting in a wicked custom cam that Jay had made for me. Slightly bigger cam. Rhoads VPro lifters. Long story short, it didn't make it through breakin. Shredded three lobes and lifters through my oil system. So I had to put the old cam and lifters back. I did keep track of what went where and lifters went in same places. Distributor gear was OK.

Anyway, when it was together again I had a hammering sound that (by its timing) seemed to be on one hole. It ramped up with load. Classic rod knock behaviour.

So, I ordered some new bearings and tore in. I was doing this all on my back in the car so after I decided #1 main looked OK I decided to just do the rods. All the rods had some scoring, of course, but journals were pretty good. None of the rods stood out at all, they were all similar. Replaced all.

Today I got it all back together and running. It sounded its old self all through the no load stuff. But when I went on a test drive I immediately had the same knocking on load. Ramps up with load. Since it sounds so much like it I didn't really push on it. I did have to complete the drive to the petrol station and back because there wasn't a good place to turn around. Big road. So, I noticed that it didn't get worse at all. So not like a lobe going flat. It also was absolutely fine with light load and cruise. The whole way. But if I had to pull away as soon as I lay in some throttle it sounded like a rod was trying to fall out of it.

So... I don't know. I can't think one journal suddenly went so away. They looked OK and similar. Bearings all new. Like I said, none of the old ones stood out from the others. So I'm a little sceptical about actual rod bearings. I just can't see how. Oil pressure good as ever. But it really ramps with load. So in my mind it has to be
* Exhaust related some how (but near a port -- either one port or the crossover on one side)
* Valvetrain related but pertaining to an exhaust valve. Can you get a collapsing lifter to sound like that?

It's really really rod knock like but I just don't see how it can be. Collapsing piston skirt? What do they sound like? Similar?

Really scratching my head. And got Street Weekend breathing down on me in like two weeks.

Sam