Is it time to replace my Oil Pump

Catfish-65

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Hello all, I have a question regarding my oil pump. When I first start my car (65 Polara with a 361ci auto) cold the oil pressure on the gauge is right at 40#s. After it warms up to180 degrees at an idle it drops to about 20#s, when I put it in gear it drops to about 12#Oil is clean and the car does not leak or smoke, Any help would be appreciated,, Thanks Dave (Catfish65)
 

Big_John

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First, try a different gauge. The accessory gauges aren't the best as far as accuracy, especially after a few years use.

Next, what oil are you using? A thicker oil may help. Changed it lately? A bypassing filter can drop the pressure. (I use Wix or NAPA Gold)

Is this pressure just at idle? Does it come up at let's say, 1000 RPM?

Low oil pressure can be attributed to a lot of things... Too much clearance in the main bearings just to toss out another cause.... An oil pump is less expensive if you want to try it, but it may not be the cause.
 

detmatt

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Even at 12 pounds you’re pumping oil throughout the engine so unless there’s other symptoms there’s really nothing to worry about. It would just be something I’d keep an eye on. Has the engine been rebuilt to your knowledge?
 

Catfish-65

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The oil is new, and it is a remote gauge not original. When driving it seems to work away at 20#s, The engine is not rebuilt and seems strong. I guess I will for now keep an eye on it. What would be an acceptable oil grade change to push pressure up a bit.. Thanks for the input,,, Dave
 

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What is the pressure when engine hot going down the freeway?

So far I see No problem, keep driving.

you don’t need 75psi
 
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detmatt

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Penngrade straight 40 weight.
 

Big_John

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The oil is new, and it is a remote gauge not original. When driving it seems to work away at 20#s, The engine is not rebuilt and seems strong. I guess I will for now keep an eye on it. What would be an acceptable oil grade change to push pressure up a bit.. Thanks for the input,,, Dave
Check it with another gauge.
 

Davea Lux

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12 lbs at idle in gear would be considered "normal"; at highway speeds, you need about 35psi. Mopars usually have very reliable oil pumps. Most of the time, low oil pressure is either too light of viscosity oil or a failing timing chain has clogged the pickup screen with debris. Check your timing chain for excessive slop. If the engine has 70k or more on it and the chain has not been replaced, it is due. Check the slop by trurning the engine over by hand until you are a TDC. Remove the distributor cap and note the position of the rotor, have a helper rock the crank back and forth with a breaker bar attached to the big nut that holds the balancer in place. If you have 15 degrees or more of crank movement before the distributor shaft moves, the timing chain is at the point of failure and needs to be replaced. The pan will also need to come off to clean the pickup screen on the oil pump.

Dave
 

413

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Valve stems seals get brittle, fall apart and get in the pickup screen also.

If this screen is partiall plugged another real good reason to NOT use thick oil.
 

73Coupe

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I recall David Vizzard (Book: How to Build Horesepower) state that about 10 psi pressure per 1000 rpm is the rule of thumb for what's needed in most engines, racing excluded.

On my non-rebuilt 440, I, too had oiling issues at sundry intervals of engine operation and driving. This was attributed to timing gear nubs clogging the pickup screen, and worn out o-rings in the pump itself.

That reminds me of another tid bit that Vizzard spoke of - most oiling problems are due to pickup problems, not pressure.
 

1970FuryConv

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Hello all, I have a question regarding my oil pump. When I first start my car (65 Polara with a 361ci auto) cold the oil pressure on the gauge is right at 40#s. After it warms up to180 degrees at an idle it drops to about 20#s, when I put it in gear it drops to about 12#Oil is clean and the car does not leak or smoke, Any help would be appreciated,, Thanks Dave (Catfish65)
I can see why the pressure would be up when the engine is cold and the oil is thicker.
I agree with all who say check the timing chain. I also agree with all who say check the pickup screen. In fuselage Mopars, a big block oil pan is easier to drop than a small block, although you still have to remove the center link and if you have a Y pipe exhaust, drop the exhaust. It's always a good practice to clean out the pickup screen in a car that you don't have much history with. It seems that every one of the pickup screens that I remove and clean out are three-quarter clogged. An extra benefit is that you can put the new oil pan gasket in, which might eliminate leaks on your garage floor.
 

Justin Plant

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Oil pumps rarely fail. Its one of the few items in the engine that is always lubed. I guess over years and years of use one could fail. But, unless the oil is really low or compromised I wouldn't worry about it. I agree with 73coupe 10 psi per 1000 is a good rule of thumb. Keep in mind the pump creates volume not pressure. Pressure comes from the tolerances between the crank and bearings. A lower quality filter can play with the numbers too. Also modern cars oil lights typically come on at 7.5 psi or less.
Just some things to consider.
 
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