Re: oil filter plumbing

Posted by HH56 On 2017/10/9 21:38:33

Yours sounds correct. The early filter with inlet on the bottom is shown in that 1943 article.

The bottom port on the block with the sender and 4 way fitting is the output of the pump. The top port is the feed to the lifter gallery. On postwar filters the inlet is on the side and the outlet is on the bottom so your car should be letting most of the oil go directly from the bottom port via the pigtail into the top port and to the lifter gallery. A small portion of the oil -- approx 10-15% or so -- goes to the filter inlet on the side of the can and the clean oil out the bottom drops into the crankcase.

On that later vol 22 bulletin where they show the plumbing the entire supply to the lifter gallery is going thru the filter just as it did back in 1940 when the 356 hydraulic lifter issue started. That route is satisfactory for solid lifters because other than the valve which admits oil into the timing chain area at the front of the gallery there is no appreciable loss. Not so with hydraulics.

The earlier issue found was with hydraulic lifters continually losing oil and needing volume and pressure to keep pumped up, along with the loss thru the valve into the timing chain area to keep the chain lubed, there was just not enough flow to do that with all the supply going thru the filter -- particularly if the filter started to get clogged. That is why they went to the pigtail to divert most flow to the lifters with the filter getting a minimal amount to just do the bypass cleaning.