I have a 1973 F-100. It has a 1972 351 Cleveland 2 BBL in it. I don't know how many miles it has on it.

When it starts, the oil pressure is 60 pounds. When it is warmed up, at idle it has 6 pounds of oil pressure. Motor heads have told me the bearings are bad. My question is, which bearings?

Main bearings? Piston arm bearings? Cam bearings?

 

It could be any and all. Usually by the time the bearings are that worn, other things in he engine need replacing/rebuilding too: timing gears, distributor bearings/bushings, piston rings, valve springs, etc. I would say it may be time for a rebuild. Good luck. k

 

First, welcome to FTE. Lot's of good knowledgeable people here.
X2 with F-250 restorer. More than likely the bottom end is worn out, thats the main and rod bearings.
Oil is thicker when cold so you have good oil pressure. As the oil warms up, it thins out. With the wider clearances from wear, the thin oil flows more easily making the oil pressure drop.
There are a few things you can do to "band aide" the problem. You can switch to a heavier grade oil, 20W50 or straight 50W. You could also add a viscosity index improver (STP or similar). A little more involved is installing a high volume (volume, not pressure) oil pump.
These are just temporary fixes to buy time but I'd say an engine rebuild is in your truck's future.
As a rule of thumb you want 10PSI of oil pressure for every 1000 RPM.

 

I'm looking for an economical solution because it is a truck I drive to do maintenance on a few rental properties. I drive about 2,500 miles a year only.

I had someone put in a new timing chain and distributor recently. The compression is high and fairly consistent and it doesn't burn oil, so the pistons, rings and heads seem OK for a work truck.

It has 17 pounds of oil pressure at 55 mph. The valves never complain so I've just been driving it. However, I'm now putting a new clutch in and have the driveshaft out, the 3 speed tranny out, the clutch and pressure plate off. Do you think I can get at the main bearings and rod bearings and replace them without taking out the motor? If so, it would be an opportune time to change the main and rod bearings now that I'm doing the clutch replacement.

The question I have is, it is a 351 Cleveland and the oil pump is at the front. Will I be able to pull it out the front? If so much is that oil pan going to have to come down before I can pull it out the front?

P.S. The idea of a crate motor did cross my mind. Is there a place I can buy a stock crate 351 cleveland motor? Summit has a 300 hp motor, but I just need a 2 bbl 351 about 200 horse.

 

To be honest, if the rest of the engine is in good shape and you drive it so little (sometimes I drive 2500 miles in less than a week), if it were mine, I would switch to the straight 50W oil first and see how that does.

As for changing the oil pump, I can't comment. I've never worked on a 351C in a truck. I have changed the oil pump in a 360 (also front mounted). I had to jack the engine up to remove the pan but overall it wasn't all that bad.

 

351/400's are early "graveyard" recipients.....they already overheat as is.....030 overbore forget about it.

They also suffer from oil starvation issues too, look at the engine schematic...they were/are junk emissions engines.

Never meant for big power...

TMI?

 

Do you think I can get to the main and rod bearings (replace them) with the motor still in the truck?

 

Two wheeler is going to tough. Tranny is out, your almost there.

 

4X4 probably. 2wd Probably not without lifting the engine a bit.

I would probably just try the 50wt or Lucas/STP additive before I went crazy. If that doesn't work, then look for a reman/crate motor. I got my 400 with TMeyer flat top pistons and a cam for $2k delivered to my loading dock at work. A completely stock long block was a little over $1600 with a 5 year warranty if I remember right. Your "graveyard" 351 made it 41 years with its horrific oiling issues and overheating so you would probably be ok replacing it with another. Unless of course you have to compensate for something else.

 

My 351M does the same. Pressure starts off in the center of the gauge, and then within 10 minutes its at the extreme low end. Always has worried me, but now I know what is going on. I did start adding heavier oil in the summer. I think I need to try and get the temp gauge to work. Pretty sure I have overheated once or twice.

Also if my foot gets heavy, I spray oil from the valve cover vent... figured the return path for the oil was slightly blocked. Causing too much oil and pressure in the valve covers.

 

 

Or the baffle is missing.

 

Could be... there are so many problems that I dont even know about or understand yet. Im knockin em out and learning. Thanks for the tip! I'll look at that.

 

What he said ^

 

Typical 351/400....junk motors....