I recently acquired a '72 F250 with a 390. The oil pressure seems a bit low. When the engine is up to temperature, it has about five pounds of pressure at idle. On the highway at 55 mph and 2500 rpm, it only has about 22 pounds of pressure.
I know the bearings are worn, but can I make it last a bit longer by replacing the oil pump? Should I use a high pressure pump, high volume, or would a new plain-jane pump be enough to boost the pressure?
I'm trying to make the engine last long enough to get another one rebuilt.

 

I have a 351-M that had the same problem. I put in a new high volume oil pump and used a thermostat that makes the engine run a little cooler, this seemed to help a little, but not enough. I'm going to tear the engine apart this weekend and put new main bearings in, it's really not too hard if you know what you're doing. Good Luck!

 

I had a talk about oil pressure in my 390 with my speed shop guru. I have valve train noise I'd like to get rid of but I'm not sure if my lifters are pumping up all the way. He said that the sensor for oil pressure is taken right after the filter and before a restrictive bend leading to the main bearings. In other words, the pressure reading comes before the oil has gone through any bearings. In his opinion that means the oil pressure reading is of little value beyond warning you of iminent catastrophic issues. I have a toasted 302 that had a bent crank with substantial main and rod bearing wear, and the crank was "walking" (a bunch). Yet, the oil pressure readings I got from a mechanical gauge, read around 60 when cold to 20ish idleing warm. If you grab your balancer, can you pull the crank in and out more than .010"? My 302 crank could be moved around .25". I am currently running straight 30weight in my 390. When the oil is cold it reads near max on the stock gauge. When the oil is up to temp, it reads just under midway at an idle. I think I have more valve train noise warm. I did a complete top end job but left the shortblock alone (I replaced cam and lifters, timing chain) I didn't do all the preload measurements when assembling the valve train. I am considering buying Crane Cams retrofit to adjustable valvetrain. I may have to get a fresh shortblock. I am also considering going to 10-40w oil. I want to get my 76 (the Big Brown Truck) back on the road but I still haven't figured out whether to swap in the 390 or go with a Windsor setup. The easiest road would be to put a 302 back in it. It looks to me like your 390 may need a lower rebuild soon.

 

Try shimming the pressure spring, it should raise the oil pressure. On top of that, run heavier weight oil, this will help cushion the bearings.

 

390, From all that I know about the FE you are still in the ok window with a well used engine. There has a lot of discussion about that on this list.

My suggestion is to keep plenty of oil in the truck. Straight 30 wt. oil is what that engine was designed to use. A 10w30 or 10w40 should meet all the engine's needs. Thicker oil may raise the pressure, but it is harder to push through. That's why it goes higher when used.

Good Ford truckin to you,

John

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

Have the same problem with my 460. (no wonder I got it for $700.) When I first got the truck from the old guy we took it for a ride and he didn't want to be on the road too long, he knew the oil pressure would drop. Anyway the first thing I did was to raise the engine and put in a new pump (rebuilt), this is not a hard job, just time consuming. Now the oil pressure is good and it takes away alot of worry for the time being undtil I get time to do the lowers. The motor has 168k on it and is all original 'cept for the pump. It is a cheap temp fix if you need one. I think the pump itself was around $30. Good Luck

 

I have fixed several FE engines with this problem. My recommendation is to install a HV oil pump and new main & rod bearings. I NEVER install a standard volume oil pump, as the HV pump will help maintain oil pressure as the bearings wear. I also enlarge (drill out) the RESTRICTIVE oil passage that goes from the pump to the oil filter adapter. Now, all of them have 60-70psi running and about 45 psi idling.

Art