Only puzzle to me is the fuel buildup on top of the intake valve and on the piston - that’s like 2-3 tablespoons on top of the piston.
That carburator was leaking/dripping. A small drip while runnig isn’t going to cause a lot of trouble but each time the engine is shut off the fuel will run down the lowest part of the manifold and accumulate on the closed valve or in the cylinder. This will wash the oil from the cylinder wall and pollute the oil.
This should have been corrected before damage was allowed to occur. If the engine shop offers engine installation that would have been the way to go. They are likely better qualified to get a new engine in the proper state of tune.
Thought I’d post the results of the compression and leak-down test. Tests were done with the engine cold - I know its supposed to be warm, but intake is taken off for now and just wanted to get some quick results:
The numbers are great although the 20% figure on the one cylinder may be a bit much.
That being said, it is entirely possible to have 190 or 200 PSI compression on a cylinder and yet that cylinder will blow oil past the rings like crazy as that has to do with cylinder wall glazing, crosshatching not quite right, rings installed upside down, etc.
Hopefully sorting out the crankcase venting will cure things but I’m not optimistic.
Oil rings can be VERY tricky to install, especially the 3-piece type with an expander that loves to get out of position…But lets not talk about that until the other issues are resolved and another start-up attempted…
I’m with OK4450 on this. The compression can be good and oil passing the oil rings.
Honestly, I don’t think anything the OP does for the PCV system will affect the problem one iota. It’d be nice if I were wrong, and for the record I hope I am, but I ain’t buyin’ it. The engine needs to be opened up, the cylinders inspected and possibly re-honed, and the pistons reinstalled with properly gapped rings. Until the OP “bites the bullet”, I think he’s gong to keep struggling with the problems.
One tipoff for me is that dramatically different conditions of the individual plugs. Causes such as bed metering and PCV problems are highly unlikely to affect the different cylinders that differently.
Sorry, but I truly think that after chasing all these ghosts the OP is going to end up pulling the pistons.
Slightly unrelated and I certainly don’t think the following applies but one time I installed a remanufactured 350 longblock in a Chevy pickup.
That engine burned through a quart of oil every 10 miles and after a 100 miles it was very apparent that it wasn’t due to a break-in process.
This led to a little volatile back and forth with the engine remanufacturer and long story short; it was determined that engine had been assembled with all of the compression rings but did not have a single oil wiper ring on any of the 8 pistons.
Disgruntled employee on the way out the door? Employee whose mind was out to lunch? Who knows; but I would suspect the former.
It would be worth cleaning up that PCV system before tearing the engine down…The vacuum port being used was meant for the power-brake booster not the PCV…The valve itself, down in the valley, MUST have an oil trap protecting it. The OP has not revealed whether the valve was protected or not…It’s a simple matter of turning the manifold over and looking at it…
There is another explanation for the big differences in the plugs, the spark plug wires were not in the right order, but if that was the case, the engine would have been very rough and had no power. BTW, you cannot just go by the firing order on the manifold, you have to know how the manufacturer numbers its cylinders. They don’t all do it the same.
I think it might actually be a PCV issue after all. There is some sort of baffle plate (though it doesnt look like it would be very effective) under the intake where the PCV valve draws from, but an AMC guy who has assembled many engines came into the shop and said it was missing a special baffle pan that AMC makes that installs in that location. Not sure where to get one. You can’t buy them, but are supposed to pull them off the old iron intakes and install them on aftermarket intakes, with a valley pan gasket. I did a search on AMC forums and it seems like many others had very similar symptoms from this exact same issue - PCV sucking up a ton of oil w/o the original baffle pan installed.
In my case, I think the problem was exacerbated as it was dumping only into to cylinders, rather than distributed evenly to all 8.
Another possibility is a “catch can”, a small tank between the valve cover and the PCV valve to collect liquid oil and oil mist.
It will need to be periodically emptied.