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69 AMX - new motor problem

If the carb was flooding that bad, the engine would not run. It certainly would not idle. it would be impossible to start…

Obscure things…In many engines, the connecting rods are drilled so oil squirts up into the underside of the piston (for cooling) lubricating the wrist-pin, and spraying oil onto the upper cylinder walls…How the rods are installed determines the direction the oil will be squirted…

Yeah… that is the puzzle to me. If it was flooding the engine that bad, it wouldn’t have started so easily and idled fine. If it wasn’t flooding though, how did all the gas get into the oil, on top of the intake valve, and on top of the piston?

Are you sure it’s GAS ? Has the oil level on the dip-stick changed at all ?

Go back and take a hard look at that PCV system…Modern V8 engines (like yours) use a “duel plane” intake manifold. With a two or four barrel carb, half the carb feeds 4 cylinders and the other side feeds the other four cylinders. So if it’s a carb problem, it will effect at least four cylinders, not just one or two…

Maybe the fouled-plug cylinder stopped firing and provided the gas to the crankcase. When my Dad’s '63 Dodge 383 was running on 7, the only way I could tell was a poof-poof-poof out its exhaust pipe at idle.

Pretty sure its gas. Didn’t check the oil level before it was drained - wish I had. All I can say is the oil is black/muddy and smells like gasoline. For the PCV valve: it is a duel plan intake manifold as you mentioned - the PCV valve is connected directly onto one side of the intake, that feeds directly into #8, and feeds a little less directly into #5. Both 5 and 8 are on opposite sides, directly across from eachother.

I think the problem can be traced back to that PVC set-up…The valve is drawing from the valley under the intake manifold…That’s okay, but there MUST be a multi-stage baffle or oil trap to prevent splash oil from being drawn into the valve !! Oil is flying everywhere inside that valley compartment !

8 and #5 are on the same plane of the manifold so those two cylinders get the bulk of the PCV flow and it looks like that flow is FULL of oil…

PCV systems work better when all the cylinders share the PCV flow equally…

SO…Does that PCV port have an oil-trap under it or is it just a hole into the valley ??

I will have to check on whether it has an oil-trap or is just a hole… should be able to find out tomorrow.

If there is no oil trap then you have found your immediate problem…Edelbrock should able to supply one…The piston and cylinder scuffing looks relatively minor but time will tell…

The motor oil looked pretty nasty for an engine with only 30 miles on it…Do you have any explanation for that? Perhaps the “boil-out” was not as thorough as you had hoped…

+1 @Caddyman. Can the engine be test-run with the intake manifold hole plugged and a tube on the PCV valve run to the ground (new sparkplugs and oil, of course)?

Yes, it can. That’s actually what the engine builder suggested and is going to do next week. Would it be worth it to do a compression and leak-down test first though?

I’d say at least compression, because it’s so simple and quick.

I THINK in the original system, the PCV plugged into one valve cover, which had an oil trap inside, and the opposite valve cover had a crankcase air intake line connected to the air filter. Using the valley as a location for the PCV is okay, but then BOTH valve covers should have fresh-air intakes to prevent condensation from forming there. In purely racing engines, crankcase ventilation can be pretty crude and simple…

Just got off phone with mechanic that installed engine. For the PVC, he said there should be a breathing baffle there, but I need to check on this.

Here is some more info, he told me this when I picked up the car, but I didn’t remember the details:
When the engine was first started, it had decent oil pressure (60-65psi). He locked down timing and kept RPM at 2000, seemed like everything was doing ok. Once everything was warm oil pressure stabilized at 50 PSI. Engine sounded fine.

He took it for a ride after 20+ min break-in, and oil pressure went up to 55-60psi @ 3500 RPMs. As soon as he let of throttle, oil pressure tanked down to 0. He was right by the shop, and coasted back.

He let engine cool down, pulled release spring out, and put in a stronger spring w/ correct seal. Started car back up, oil pressure was at 100 psi. As it warmed up, the oil pressure started to drop down to 80, then 60, then 40 when engine was idling and warmed up.

He said this was just a patch, and needed to be addressed. When I took the car, oil pressure was around 80-90 w/ throttle down, but then was dropping down to 35 PSI on deceleration.

Winston Churchill, in his first wartime broadcast:

“I cannot forecast to you the action of Russia. It is a riddle wrapped in mystery inside an enigma; but perhaps there is a key.”

Wrapped in cast iron?

Increasing the oil pressure relief valve spring tension will not affect low oil pressure due to oil clearance in the bearing journals. The oil pump and relief valve are in the timing cover so the spring is easily replaced but if pressure drops as the oil heats oil pump volume would need to be increased, not the pressure " limiting" spring.

It would be a good idea to run both a dry and wet compression test. That oil pressure to zero event and the subsequent modification is closing the barn door after the horses escaped.

Scored cylinder(s) generally means overheating or lack of oil and that generally means scored rings and pistons.

It’s possible this engine may have to be gone through again with the debateable point being who is going to cover it.

Yeah I think that is going to be the debatable thing here - who is going to cover it… fun. That’s why I want to get as much info as possible to understand where the original problem came from.

The oil fouled plugs, oil pooling and piston scoring does not look good. What I would take issue with is that the shop apparently had a problem crop up and handed it back to you with what is described as a patch.

Whether the “coasted into the shop” right after the oil pressure drop story may or may not be true and when big money is involved it can be quite common for someone to revert to self-preservation mode.

It’s difficult to tell from the picture but is there any oil pooling in the valve train area of the cylinder heads near the rocker arms, etc? It looked dry but that could just be me.

Is there any question as to who is at fault here? The engine builder is responsible. You said they are reputable. They should stand Behring their work then. Even a pro has a bad day every now and then.

Yeah I think he will stand behind his work, his concern though is that the problem was caused by overfueling or from where the PCV valve was installed.