Quote:
Pretty sure all these filters assumed flow from outside to inside
You would think so but not the case. The Purolator filters Packard used prewar (also sold aftermarket) had a bottom inlet and all the oil went inside to outside. There were issues with hydraulic lifters in 356 engines when the filters clogged too early even soon after being changed so Packard issued special elements, then went to a canister with a relief valve that would open and bypass the filter entirely if clogged and finally revised the plumbing so the lifters got a direct unfiltered flow from the supply port coming straight from the pump. That is when they started dumping the filtered return oil straight into the crankcase.
After the war they reversed filter flow and went outside to inside and kept the final version of the prewar plumbing on the 356. For whatever reason they went back to the filter outlet going to the lifter port on the early 288/327 blocks. I suppose it was probably because the 288 replaced the 282 which had solid lifters and the same setup. With the 288 and the early 327s only available with solid lifters I guess they figured it would be fine. When hydraulic lifters started to be the norm instead of an option on those engines they finally saw the light and starting in 51 put the return port in the block on the smaller engines too.. That same basic plumbing setup and outside to inside filter flow lasted thru 56.
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