351W Low Oil Pressure

[mickl]

Hi Guys,

I have a 71 with a 1979 351W in it. Had the engine rebuilt about 7 years ago, but I haven't even put 10k on it. I've noticed that the oil pressure is good when I first start it up. As I drive it, the pressure starts decreasing. I drove about 20 miles and when I was almost home I was sitting at a light and the gauge was almost on "L". I'm not sure if the oil pump was replaced when the engine was rebuilt. The engine runs just fine and no smoke....sounds pretty strong when idling. I do have to replace the doughnut gasket on the right side which is causing an exhaust leak for me. When I'm going down the road, the engine sorta sounds like a sewing machine which I don't like too much.....guess this due to the exhaust leak. I just wish I knew how to setup the engine properly. On the left valve cover, there is a little valve that I guess a hose is supposed to connect to and run to the air filter, but I'm not sure how to set that up properly (know where I can get a manual for the 351W?). Jeez, wish I knew a lot more about working on engines and trucks in general. I really like this old truck (was my dad's before he passed away) and would rather drive it than most of this new stuff now.

Thanks for the advice and help. Anybody from California around the Yuba City/Marysville area that knows a good electrical shop. I need to get some things rewired properly.

Thanks,
Mike

[BobbyFord]

Check it with a mechanical gauge while warm to verify if your gauge is accurate.

[mickl]

Thanks, I'll do a search on this to find out how to do this, or if you have time to explain....I'm all ears...

Seems that the gauge is working (not sure how properly working it is) because it starts high and then decreases as the engine warms.....

[FORDification]

When engine oil is cold, it's thick and will produce more pressure than when it gets hot and thins out. Low oil pressure is typically caused by increased clearances in the main and cam bearings due to wear. However, I wouldn't rule this out in your case, even though you say the engine has less than 10K miles. If the new engine was assembled with the proper clearances, they should be OK, but not all engine builders replace cam bearings (though they should) or assemble an engine with the proper clearances.

Folks typically run thicker-weight oil in the summer or in warmer climates to increase oil pressure, and switch to a thinner-grade oil in colder climates.

I'd follow Bobbyford's advice and get a mechanical pressure gauge installed to verify what the semi-inaccurate factory gauge is telling you, plus it'll give you a pressure PSI range that we can look at further.

If you're using the factory air filter assembly, the filler cap on the left-front valve cover is connected to the left side of the filter housing with a hose. This is a picture of an FE, but the concept is the same.

http://www.fordification.com/images/70explpics/16.jpg

[mickl]

Thanks for replying to my post. I'll see what I can do regarding the pressure gauge. Thanks for the pic. Very nice engine....