390 low oil pressure

[Commodore Woods]

Hey I've got a 72 390 in my F100 Ranger XLT, My oil pressure seems to be pretty low when I'm at an idle and she's all warmed up, I've got a friend that's really into Fords and he was saying that it might be the Valve guides in the head passing oil, my dad and I were thinking that it might also be the bearings in the bottom end getting old and worn, passing oil. What do you guys think?

[DuckRyder]

How low? They will run for ever even with the oil light flickering at hot idle, although I wouldn't advise it.

Probably cam bearings.

[Commodore Woods]

All I have is the pressure gauge no light, When I first fire it up in the morning and the oil is cold it runs at our about halfway down the gauge right along the "I" in Oil after it warms up it runs right about halfway through the "O"

[DuckRyder]

I would put a mechanical gauge on it. They are reasonably inexpensive.

As long as it has more than 8 lbs at idle (the warning light switch trips at seven on trucks with a light) and it maintains 25 or more at cruising speed, I would not worry too much about unless it shows other signs of problems. Once you verify this, you can return the regular sender and remove the mechanic gauge.

Then you know what the positions on the ford gauge really mean.

It also might help to run an extra quart.

[oldschoolrods]

A good rule to follow is 10 psi per thousand rpms.

[fordfanatic]

Is it smoking?. My engine has about 317,000 miles on it, and it started smoking real bad. It had been smoking for a couple of years just at start-up and then would quit once warmed up. I put new valve seals in it, and of course cleaned up my rocker shafts(bad mistake) they were so worn that now I have only 3psi. of pressure at hot idle. I believe I have worn valve guides, and possible ring problem I'm not ready for my rebuild yet, so I may put some guides and rings in it for now, and see if I can reduce the smoking problem. Sorry to run on, as far as your problem, if your pressure stays low and you're not ready for a rebuild yet, then the next o/c you do I would use 20-50 and add one bottle of Lucas oil stabalizer in place of a quart of oil, and your pressure should increase by 5psi. or so at hot idle. Chris

[Commodore Woods]

I'm not really smoking at all, I need to put a gauge on it, the only other signs of problems with oil are a bunch of leaks ( distributor, Intake to base plate of carb, oil pan, and probably a couple other unkowns)

[Faithful Old Road Dog]

I had a 67 F100 with a 352. It had lots of miles on it. As years went by, the factory oil pressure gauge got lower and lower. I'm talking near or below the line on the factory gauge. I pulled the valve covers once to change the gaskets and saw all the built up crust. I left the crust alone as I figured chipping out that stuff would be worse. Any bit of crust that let loose could have chewed up bearings. I didn't have the money for a rebuild and didn't feel like investing the money for a rebuild as I really wanted a highboy. My trick was to use Valvoline straight 50 wt. oil. That pumped up the pressure to read low. That was an improvement!  Then when I detected the oil pressure drop a bit more, in went Valvoline straight 60 wt. Sure it smoked, but not like a steam locomotive. 1967 is smog exempt here. It ran on 7 cylinders for years.

[flyboy2610]

[68F250]

When I first fire it up in the morning and the oil is cold it runs at our about halfway down the gauge right along the "I" in Oil after it warms up it runs right about halfway through the "O"

You are fine!  That's the way it should read, as long as it stays within the operating band (the horizontal line below the "Oil").  I wouldn't even bother putting a gauge on it.

[willowbilly3]

Those factory guages aren't reliable except as a reference point after you use a mechanical guage to verify your psi. I have a mechanical guage with a grease gun hose on it that I screw into the engines to see what they are actually doing. Many years ago I was worried that the oil pressure was a bit low on my 72 as it was just at the very low end of the normal when running down the road. That turned out to be 55 psi.

[shrektruck]

It's nice to know what your pressure is. I thought the Hayride was ready to die. Finally stuck a gage on it and it's at 38 when the dash gage has barely moved past the first line.
I had a real good buddy in Lee's Neck Farm in Virginia who used to take my old oil to run in his I-6 240. He drove it for the 5 years we were stationed together and it never blew up.

[Faithful Old Road Dog]

At least your buddy was changing the oil. But, someone should have told him to use fresh new oil.

[Commodore Woods]

I finally got a new Mechanical gauge added, this week, I was able to find a T and plummed it for both the stock and Aftermarket gauges, I wound up messing up my sending unit so I got another one for about 20 bucks, turns out the reason my pressure looked so low was a sending unit going bad anyway, my actual pressure when cruising down the road is about 23-25 PSI and just over 50 when she's all cold. (BTW I found out that there isn't a whole lot of space between the new sending unit with the T installed and the power steering pump bracket but it does fit.... barely   )