Re: '34 718 Std 8, 2/4 Coupe, Engine & Drive Train Diagram(s)

Posted by Owen_Dyneto On 2016/5/21 17:35:57

That unit is the oil pressure relief valve, actually 2 valves. The adjustment screw under the acorn nut adjusts the maximum main oil pressure to a "not to exceed" pressure, 55 or 60 psi is the correct adjustment. The 2nd valve (under the hex cap) is unadjustable and will function to allow normal engine lubrication in the event the filter should clog. The two lines you see are from the pump outlet thru the relief valve to the filter, then thru the cooler and return from the cooler back the engine's internal main oil gallery.

Quite unique for the time and first appearing on Packard in 1934 is this "full flow" oil system, meaning that 100% of the oil that leaves the oil pump is filtered before reaching the engine internals. Packard retained this system on the 320 and 385 cubic inch Eights and Super Eights and Twelve engines thru 1939 but thereafter returned to simplier "bypass" filter systems, meaning only a portion of the oil leaving the pump is passed thru the filter. In modern engines of today full-flow filtration is the norm.

Nothing uncommon in any of this, though in later engines of the postwar era and newer the pressure relief valve is normally inside the oil pan and not accessible.