Posted by clueless [201.202.24.222] on Friday, November 20, 2015 at 10:47:39 :
Bypass Oil Filter
One option found on almost all flathead mopars is a bypass filter kit. The factory version was a Mopar Oil Filter Kit available in two versions, replaceable cartridge filter inside a filter housing (Mopar # 1123-152) or a non-cleanable canister (Mopar # 861-028). The first type is more economical to operate as all you need is a replacement filter. They are readily available from suppliers such as NAPA. Installation and operation is unlike today's full flow oil filters. Numerous other manufacturer’s such as AC or Purolator also offered aftermarket versions. These are "bypass" filter systems, which means they only filter and circulate oil through the filter when a specified oil pressure is reached. Below that pressure the oil filter circuit was bypassed by a valve in the oil pressure relief valve. It is a good idea to verify the kit is correctly installed. Filters have line connectors which are stamped "Inlet" and "Outlet". The inlet is plumbed to the oil galley on the side of the block. They would put it under pressure to fill the filter case. The return line (Outlet) goes to the fitting on top of the oil pressure relief valve. In the P15 Parts List manual, page 174, is a drawing illustrating a standard installation. The Plymouth Service Manual ('46-'54) on page 153 provides an explanation of how the filter works. When the oil pressure relief valve is closed the oil pump fills the oil line and oil filter. The relief valve blocks oil flow FROM the filter to the crankcase. When the oil pressure is greater than relief valve spring tension, the valve starts to open. Excess (clean) oil then returns form the filter to crankcase. The relief valve opens a passage for the oil to flow from the filter to crankcase. Because the filtering operation is dependent upon proper and timely operation of the oil pressure relief valve, the quantity of oil cleaned is substantially less when compared to a modern full flow filter. The size of the oil line is approximately 25% of what is found on a modern filter so the volume of oil when the pressure relief valve is open is also much lower. While filtering may longer than a modern full flow spin on filter, the level of filtering is much higher than a full flow. Because of this they provide excellent protection for your engine's components.
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