So, I woke up this morning with, I think, a clearer head. I have a pretty good guess at a cause that fits all the evidence. I think I have some trash in an oil passage.
Hear me out. What if the old rod bearing knock was rod bearing knock (like it sounds) but the bearing wasn't really damaged yet? I mean, I've never given it much throttle after I hear the noise. I was thinking knock because the bearing is already pounded (like detonation) but what if it is knock because LOCALLY I don't have enough oil pressure. Because THAT PARTICULAR pressurised oil feed is weak from partial blockage. There would still be some supply. But weak. I would only hammer it under load. As soon as I do I stop and I haven't done it much so the bearing looks OK (because it mostly still is). I put in new bearings and it still knocks because the supply is still weak. The clearance is fine but the oil pressure for that rod bearing isn't?
What do you think?
I've been pondering on
(from my shop manual)
I could be starving (partially) some of this passage from oil galley to #5 main. Main probably won't care as much with other mains fully pressurised. Or it could be in the crank from main to that rod bearing (although those are bigger passages so I kinda doubt that part).
Anyway, that's my current best theory. Rods and bolts and rod bearings look OK because the are. I do have great oil pressure. 60psi at hot idle with 5W-30 oil so I'm not surprised if a partial blockage doesn't have much symptoms until more load is applied.
Well, if I were right I'd definitely need to pull the whole engine. Would need to lift the crank out and can't do that in the car.
I have a garage but not an engine hoist. I can rent one. But the garage has a pit. Now I thought that was a great feature until I found that it is always flooding and you have to be a midget to stand in it. What it mainly does is make jacking the car a pain in the arse because the boards can't take a lot of direct pressure. But I'm pretty sure I could wheel an engine hoist in there. Just trying to think through the minimum I would need.
* Rent hoist
* Gaskets
* Rod bearings again
* New rod bolts if I'm smart
* More oil
* More coolant
By the way, checking the oil on this car is now hilarious. With iike three oil changes in a row in a few hundred miles the oil is basically invisible on the dipstick. My engine may be undriveable but it is the cleanest undriveable Pontiac 455 on God's green Earth.
What do you think? Not sure I can get this all done in time but also maybe I can..
Sam