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Old 09-28-2021, 02:22 PM   #1
william.sykes@att.net
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Default low oil pressure

I'm a new guy with V-8 Flathead Fords. I have a 1946 Ford 239 cu. in. which I believe is the original engine with 64,000 miles. Upon starting, I have 40 psi oil pressure at idle and approx. 70 psi at road speed measured with a mechanical gauge. I'm running 20w-50 oil and I have installed the .063 restriction in the inlet side of the oil filter. When the oil gets to operating temperature, the pressure drops to 5 psi at road speed and 0 psi at idle. The engine runs great with no smoke and no unusual noise. I plan to eventually drop and clean the pan and install a fresh oil pump. Any thoughts?
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Old 09-28-2021, 03:17 PM   #2
alanwoodieman
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Default Re: low oil pressure

oil pressure relief spring is bad
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Old 09-28-2021, 11:47 PM   #3
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Default Re: low oil pressure

The main thing is to see pressure at rpm when HOT, you can go by the 10 lbs per 1000 rpm . It's not uncommon to see almost zero (and that will depend on your gauge) at idle.
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Old 09-29-2021, 05:44 AM   #4
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Default Re: low oil pressure

I wouldn't be too quick with a replacement oil pump. Pull the pan and remove any accumulated crud from it and the oil pickup. Might be everything needed. The oil pump isn't a typical wear item.
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Old 09-29-2021, 02:28 PM   #5
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Default Re: low oil pressure

One thing for sure - 5 psi at road speed is not enough . . . so until you fix the issue, I'd not be doing that.

As noted, I would pull the pan first and check/clean it all out . . . and probably think about a new (later) oil pump. You can put an 8BA pump in it with the necessary pickup for the early pan. You can buy the pickup at Speedway - which beats the heck out of having to cut, splice, weld up the later pickup for usage in the early motor.

Pickup: (without the screen - they can supply with the screen).

https://www.speedwaymotors.com/Speed...Tube,4289.html
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Old 09-29-2021, 08:24 PM   #6
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Default Re: low oil pressure

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Are your readings from an original dash gauge? if so, they tend to be quite inaccurate. you might want to add a modern direct reading gauge (you can put a "t" in the oil line where it enters the oil filter, if you have one). if it reads differently from your dash guage, you can mentally calibrate what 5lbs on dash means. the aux gauge does not have to be readiily visible if you want to maint stock look.
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Old 09-29-2021, 09:00 PM   #7
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Default Re: low oil pressure

Readings were taken with a modern direct reading mechanical gauge.
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