Surprised to find that a 1/4" flare to NPT fitting on the "input" side of the remote spin-on filter (Franklin 165 - Cruisair) is restricted to 0.035". This fitting is sourced by the oil-bypass plate. The fitting on the output side of the filter is unrestricted and is tapped into the sump drain fitting. The 1/4" input side fitting has some bad threads on the flare and I'd like it replaced, but want to understand if the restriction is necessary - perhaps to reduce pressure at the filter. Just seems like a hole this small could clog and prevent the filter from doing its job. The previous owner was using a Fram PB50 filter. The filter bracket does not appear to be the Airwolf or the ADC part - looking through the logs now to try and identify it. Bill
Restrictor in the remote filter oil line
- Thread starter blanducci
- Start date
Ralph925
New member
The small orifice bleeds some oil out of the gallery leading away from the pressure side of the oil pump before it gets to the bearings. This oil is “bypassed” around the engine and run through the filter (making this a bypass filter rather than the more modern full flow filter). Removing the orifice will let all of the oil bypass the engine bearings… :shock: probably not a great idea.
I don’t remember the orifice on mine being quite this small. Is it possible the gage and oil filter lines have been switched?
I don’t remember the orifice on mine being quite this small. Is it possible the gage and oil filter lines have been switched?
That makes sense. I'm replacing the bad restrictor with a new one with the same orifice. Long term plan I think will be to have the bypass system replaced by the Airwolf setup that puts the filter in series with the cooler for full filtration. Curious that this wasn't the norm when folks first started putting filters on these. Some downside? Larger, potentially longer hoses, and puts the filter in a critical path is all I can think of.
SoCalPlaneDoc
New member
blanducci said:
the air-cooled VW dunebuggy crowd used to do that since most of the oil was by-passed and a clogged filter wouldn't ruin you day...