Re: Standard 8 '49 - oil pressure

Posted by Tim Cole On 2008/2/27 18:56:50

Hi Henrik:

The manual specifies maximum oil pressure of 40 psi with 5-15 psi at idle. If oil pressure at 35-40 mph is below 20 psi a mechanical problem is indicated.

Now the tap on the side of the engine is a calibrated orifice and not representative of true mainline pressure. Thus, the sender is engineered with a correction factor.
Thus, if you hook up a gauge to the sender tap you may think that you have low oil pressure until you look in the manual as to what the gauge reading should be at this point in the system.

Packard made some explicit recommendations against running too much oil pressure. The general rule is 10 psi per 1000 rpm with no more than 10 psi times the maximum rpm for the engine. This is very close to the Packard maximum of 40 psi if you consider that the eight revs up to about 4600 rpm with throttle wide open.

Here is a little test for mainline oil pressure: accelerate in second gear to passing speeds, if you start to hear noises from under the hood that may be worn rod bearings (especially if the noises don't start until then engine is hot). If your engine runs quiet then you have little to be concerned about.

If your engine is worn then take it easy and keep the road speeds modest. You may still go a long way with worn rods bearings given you don't push it. No guarantees of course.