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Oil pressure irregular

yatesjr

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I just put 10w-30 in my 1969 383. I’m not sure what oil was in it before but I didn’t seem to have any issues. I hooked a mechanical gauge up and the line filled with oil and held 75 at cold temps. However, when the engine is cold now at idle I hold 28 pounds and the oil line to the gauge won’t be full of oil but has some like pictured if I hit the gas it’ll jump to 55, full the line and stay while on the throttle. When the engine is hot at idle the line isn’t full of oil like at cold idle and the gauge-sits at 0. Not sure what it’s like when driving and it’s hot as the gauge is in the engine bay since I just hooked it up. Could this mean I need a 20w-50 oil or could it be my oil pump or bearings? I don’t understand why I have no pressure when it’s hot and why the line isn’t full of oil

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I would verify that that gauge is correct just to be sure. But it does sound like you have an oil supply issue. Its not the heavier weight of oil that's going to fix the problem. Zero is not good.
 
What's in that space that's clear in the oil line ? Does it remain the same, or does the size of the gap in the oil line change ?
 
I would say the increase in pressure compresses the air, causing the oil to more completely fill the tubing and vise versa at low RPM. Boyle's Law. Basic physics.
Mike
 
Is this the same gauge as before? now after the oi change it reads low? Almost every mechanical gauge has air the line. You are talking a very small amount of volume. At a given pressure the air in the gauge will compress and read near the same pressure as if it had no air. If it's the same gauge and now it reads zero I'd suspect either the filter #1. Or posibly the relief valve being stuck partialy open #2.
Doug
 
What's in that space that's clear in the oil line ? Does it remain the same, or does the size of the gap in the oil line change ?
It changes. I assume it’s air? When I hit the gas the whole line fills with oil
 
Is this the same gauge as before? now after the oi change it reads low? Almost every mechanical gauge has air the line. You are talking a very small amount of volume. At a given pressure the air in the gauge will compress and read near the same pressure as if it had no air. If it's the same gauge and now it reads zero I'd suspect either the filter #1. Or posibly the relief valve being stuck partialy open #2.
Doug
Yes same gauge. Can I check those to see if they are the issue or do they need replaced?
 
did you replace the oil filter with the same one.
 
Yes same gauge. Can I check those to see if they are the issue or do they need replaced?
I'd swap the oil filter before anything. If that doesn't help you can access the relief valve in the car.
Doug
 
Loosen the line fitting at the gauge and bleed off the air. It will be messy.
Mike
 
I recently had a problem with my engine not picking up oil pressure. Long story, short, I replaced the Fram filter with a Wix, on the advice of a racing buddy. After doing that, the engine picked up a prime and runs 70 psi. cold.
 
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Loosen the line fitting at the gauge and bleed off the air. It will be messy.
Mike
You will never bleed the air out. After the engine shuts off, the oil galleries drain and refill with air. When the engine starts up again, the oil pressure fills the gauge line back up with air. The gallery oil compresses this air to the same pressure as the oil, so the gauge reads the right pressure. There will always be some air in the gauge capillary tube. If you don't like to see this, put a copper line on the gauge instead of the clear plastic one.
 
What filter did you use? Wix seems to be ok. Fram, maybe not good. Dave6T4 taught us that.
 
did you replace the oil filter with the same one.
i was thinking more if it was the right one not the brand. when i got my car oil pressure would not go over 30 lbs they had the wrong filter on it.
 
Like posted above. Change the filter to a wix or napa gold and add back lost oil.
10/30 is ok for weight.
And if that gauge is going to be on or in the car, go with a copper or braided line.
 
Like posted above. Change the filter to a wix or napa gold and add back lost oil.
10/30 is ok for weight.
And if that gauge is going to be on or in the car, go with a copper or braided line.
I’m not sure what oil was in the car before I drained it could do 20/50
 
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