RB Oil Pressure

Furyous 64

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I received enough good advice on troubleshooting my oil pressure problem searching old threads, I figure I may as well join. Regarding the oil pressure, it suddenly went to "0" on a 40k RB that has always maintained excellent OP. No Oil from the pressure sensor port. No knocking, but valve noise. longer story abridged, Pulled the right side valve cover and then see #4 pushrods (both) bent to hell, one with a near 20deg angle on one end. Both lifters out of the bores and laying in the valley. tried to pull them out with a magnet but no luck, so I guess I'm pulling the intake next weekend. Here's the remaining question(s).
-- Assuming i lost oil pressure when the lifters left the bores and no longer maintained pressurized oil routing through the Rt gallery to the crossover correct?
-- I'm guessing a stuck/sticky lifter(s) bent the pushrods, valve springs look good, haven't been able to get a compressor on the valves to test they open, but they look ok, rockers look fine. Should i be suspicious of that diagnosis and continue looking? engine was idling when I think I heard pushrods bend (hindsight), drove 1/2m home with good oil pressure but a miss. changed plugs in hopes of fixing the miss and after startup, noticed valve noise and then saw the pressure gauge, shut right down
-- I'm thinking about just ordering a new set of lifters and pushrods and pressing on unless I find anything else, but I'd like to be more confident, any place I should look at specifically? I'd rather not pull the heads, but if necessary...


Thanks in advance
1964 Ply Fury 426W (not a maxxie)
 

Lefty71

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If it were me, especially on a vintage 426.... I'd pull it down and look at literally everything before attempting to run it again.
 

R413

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Has the car been sitting.
And does it have old fuel in it.

valves sticking in the guides will do this.
 

RemCharger

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Has the car been sitting.
And does it have old fuel in it.

valves sticking in the guides will do this.
Totally agree. The last 4 engines I've torn down all had a couple rusted/seized valves.
Might run for a bit until they got hot.
 

Fran Blacker

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You heard push rods bend and had oil pressure, the lifters were still in the bores. As noted above stuck valves.
 

Furyous 64

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Has the car been sitting.
And does it have old fuel in it.

valves sticking in the guides will do this.
I don't drive it a ton in the summer (no AC in So NM) but it hadn't sat more than a month or two. Pretty sure I'd filled the tank last time I drove it. I typically drive it no less than 2, 3x per month. I do plan to check the valves
 

Wietse

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The cam lobes have popped the lifters out of the bore I guess, but after the push rods went out so sticky valves seems the first reason I would look for.
Another thing to check later on is the cylinder cranking pressure.
If a valve got hit by the piston it might be bent and not sealing, you will find low/no pressure on the trouble cylinder.
 

Geoff 2

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Did you give the engine a 'big' rev? Tired valve springs will allow lifters to pump up......& you know the rest.
 

Furyous 64

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I was idling at a light when I think I heard the pushrods go. driven less than 10m after, then when I noted the oil pressure, I was idling in the garage with just a couple of gooses of the throttle to see if the miss was still there after the plug change. Tomorrow i pull the rocker shafts and manually run the valves with a spring compressor. assuming the sticking was temporary, and they free up, is there a way I can keep them from sticking again? (other than rebuilding the heads) I'm assuming if #4 valves stuck, it was cylinder fouling, not rust/seized. The plugs do foul regularly, this thermoquad tends rich. the engine doesn't sit for super long periods (it's run at least monthly) and I'm in the desert SW.
 

Wietse

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I'd put cyl #4 in TDC and remove the valve springs of both of them, put a O-ring in the retainer groove or zip-tie on the end of both valve stems and lower the piston.
Now you can move the valves by hand to confirm they are tight or not, they should slide freely without any binding.
If you can, check the valve spring load at the seated height and confirm they are in spec.
Once back together do a cylinder pressure test to confirm the valves are not bend and seal good against the seat. (in case they took a hit of the piston)
 

eldubb440

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wouldn't it be pretty odd to have 2 bend at the same time? especially on the same cylinder?
 

Wietse

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Excessive deposits, low cylinder pressure.....head gasket ==> coolant leak causing corrosion?
Knowing cylinder pressure and/or leak off test will give some confirmation of what to consider as a cause.
 

Furyous 64

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Pulled the intake and valley pan, pulled the rockers and checked each valve with a lever type spring compressor modified with a bridge to actuate the valve, not just the keeper and spring none felt "sticky", they all came off the seat and felt to re-seat just fine. put the rocker shaft back with new pushrods and turned over manually and then with the starter, all of the valve train looked to be working smoothly. I don't have leak down gauges, but with air to the cylinder, didn't hear any leaks. the good news, with the lifters back in the bores, I'm now back to 80psi of oil pressure with the drill and priming shaft, hit's 40 just turning over with the starter. but I'd really like to understand why both ex and int pushrods on one cylinder bent before I put everything back together
 

Geoff 2

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#4 is a middle cyl. I have often seen the exhaust v/springs on the two centre cyls shorter [ free length ] than the outer cyls on high mileage engines. Large concentration of heat there softens the spring. Refer to post #8.
 
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