Re: Standard 8 '49 - oil pressure

Posted by Tim Cole On 2008/2/28 20:56:57

What the manual refers to is mainline and secondary (tappet) pressure. They don't actually talk about calibrations, but what you have is an oil galley on the right side of the engine that feeds into a smaller bypass cross-channel that feeds the oil filter and tappets. That cross bored bypass is calibrated.

Thus when they talk about normal oil pressure at 45 mph being 40 psi they aren't necessarily talking about pressure at the sender. Packard seemed to like this sort of obfuscation. The earlier manuals drive me crazy with their contradictions.

I had this customer come in because his mechanical oil pressure gauge read all over the place while the dashboard gauge was mostly steady. The engine didn't knock when I pushed it up to 40-45 in second. Yet the mechanical gauge says the motor has crummy oil pressure. However at 40-45 mph the mechanical gauge is reading 25 psi while the dashboard reads 30. Next I look in the manual and see "normal oil pressure is 40 psi" but they don't say whether that is mainline or secondary. They only say that less than 20 psi is a problem. Well I do know that the mainline pressure is at least 25 psi because that is what the gauge says. My conclusion here is that the motor passes all of the minimum requirements stated in the manual and that the gauge might as well be an idiot light (it may have had the wrong sender). The purpose of the manual being to diagnose a customer complaint.

When I was overseas working for the Air Force they used to bring me these Fords that would have erratic oil pressure gauge readings - zero or middle. Well if the gauge is at zero and the motor isn't clattering it is obvious that the oil pressure is good. You wouldn't believe the trouble I had trying to convince the military that the Ford gauge was calibrated to a default value. That wasn't in any manual.