I agree its not ideal....but 351m and 400 live forever with low oil pressure. There are a ton around here going up and down the road that hold no psi at idle. I like engines to have plenty of oil pressure though..I keep a look at my gauges often. One of my buddies 400 finally started knockin....when he swamped it and filled the engine full of creek water and then still drove it before changing oil. Its now rebuilt and going again.

 

I agree that you don't have to worry. That motor will last beyond your time frame for rebuilding/replacement. Have you changed your mind about a 460? I don't have any "inspection" issues with mine(460). As long as it looks like it has the "proper" stuff in plain view they don't know the difference between a 400 and a 460... Pump, hoses, egr, factory carb, pass. No time limit on those engine stands

 

Any engine with low oil pressure is bad. There is a problem if it reads real low. No engine should read low oil pressure. If so, your bearings won't get lubricated such as those on your cam....then eventually your piston rod bearings and crank bearings which will lead to knocking then KABOOM!

 

I know that all too well since I went to diesel school for 2 years. I never said it was good....or that I want it....just simply saying some engines tolerate low oil pressure very well.

For a V8 to be fairly healthy it only needs 10psi for every 1,000 rpm.

 

I would not rely too heavily on the stock gauges. They take the pressure, convert it to electrical resistance, then a 30 year old gauge translates the resistance into needle movement. An aftermarket mechanical gauge runs the oil right to the gauge face and removes any guessing games. It's also hard to quantify oil pressure with the stock gauge. What is the PSI if the needle points to the "R" in NORMAL? It's not a useful diagnostic tool.

The rule is 10 PSI per 1000 PRM. So if your idle is set at 700 RPM, you should safely stay above 7 PSI. I believe the factory dummy lights come on at 5 PSI.

My Galaxie has a 400 in it. It has just over 150,000 miles. It finally started knocking this month. When I got it, it had 143,000 miles and the oil light flickered. When I tested it with a gauge, it had maybe 30 PSI at WOT, and almost zero at idle. The previous owner said the light had been flickering for many miles.

The knocking came all of a sudden. No valve clatter ever, just always really low oil pressure. I had been running 20W50 and Lucas in it as a last ditch effort to keep it alive. It was fine one day, then all of a sudden the next day it started knocking while running some errands. I turned around and went home; by the time I got home the engine sounded like driving in railroad ties. Now it sits in the driveway with leaves all over it.

 

Just curious, but did you get the rear main to stop leaking? Do you think the wear on the bearings is a real problem on your truck or is the problem gone now?

 

Stock high mileage Fe's seem to live forever with oil psi idling at 5-10 psi and 20-30 psi at cruising speed.

 

Still leaking, My bearings are shot so they wont seal up tight. For now I just have to park it on the street and check the oil weekly until I replace the engine.

 

You are in good company Sir...unfortunately...

 

The Buick 231 V6 is another engine that lives on low oil pressure. Some of those Turbo (turbo no less) engines could barely muster 1 psi at idle. But they lived.

Josh