Originally Posted by Nomad Willy
"the drain back valves on any filter I have ever seen are only on the "input" side of the filter, not on the center outlet."
From that can I conclude that a horizontal filter should drain only part way if it had a drain back valve? That could be the case w mine.
Where are these drain valves located and can one see the valve and know if the filter has or does not have the drain back valve.
kchace also wrote;
"If the filter is higher than the engine (which mine are) it can always drain "forward" through the filter media and the center hole and into the oil galleries. This is probably not the best, maybe they drain down every time I shut the engines off?"
This I would like to know as if the oil drains back into the crankcase on shutdown every time one started up the filter would need to fill (and galleries ect) before oil pressure was realized at the engine bearings. It would be a strong indication that engine designers know that the lack of oil pressure during this time causes no harm or extra wear. That would confirm (perhaps) that the notion of serious engine wear at startup is serious business and promote pre-lubers. I've always thought if this was a problem pre-lubers would be standard equipment. Filters draining indicates that the notion of serious bearing wear occurring at startup is an "old wife's tale" and not valid.
Oil direction in a spin-on filter is always "into" the filter through the holes around the center hole, and filtered oil goes "out" through the center hole. The anti-drainback valve covers the input holes around the center. If you look at them and they seem covered, there is an anti-drainback valve in place. Ideally, any spin on filter would be installed with "screw up" so that it couldn't drain back helping oil pressure to come up more quickly after a cold start.