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Re: Blocking off bypass in "A" Poly

From: Hank Dozier
Remote Name:
Date: April 30, 2002


If you use a remote filter (generally a spin-on type), the filter itself has a bypass popoff valve internally to assure that if it plugs, the oil flow will not be cut off. The bypass shunt under the rear main cap between the inlet and oulet ports at the filter plate does the same thing, only it ALWAYS bypasses a little oil (unfiltered). If you change your oil regularly, then this is not an issue. You will live with some shunt flow bypassing even a remote filter. The filter's bypass popoff would probably never work because the internal one is closer, and has the delta pressure working for it (your remote has all the line loss restrictions). I would not worry about it, but later "A" polys (I think around 63 or 64) they removed the internal bypass. No engine has it now, as it is incorporated into the filter. All I state is that if you want to make sure that ALL your oil is filtered, you need to plug this bypass above the rear main cap. It is a "be aware" admonition only.


Last changed: July 19, 2018