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These are the ends of the OEM AC Delco engine oil cooler lines (12472277 and 12472278; one came with an o-ring [the outlet line for what it's worth] and one did not, but I'm not sure if that is the way they are supposed to be or if they both should have an o-ring). Is that a JIC? Or is it a metric o-ring port?
Am I correct in understanding that the engine oil cooler line end type at the radiator is different between 88-95 and 96-98 (and is that contributing to the confusion)? I have a (very late model-year 1995 Oct 16 build date) 1995 2DR 4WD 5.7L LS Tahoe.
Do I need metric o-ring port fittings on the radiator ends of my custom engine oil cooler lines (and is that in fact an M20x1.5 metric o-ring port)? Or would it work with liberally applied thread seal teflon/PTFE tape and the 20mm x 1.5 metric to -8 AN flare
adapters that I already purchased (as I wishfully thought it might)?
(So far I've found several of, while the the appropriate type what I believe to be, incompatibly-sized M16x1.5 to -6AN flare
adapters. When I search o-ring port adapter some have the o-ring on the nipple end [like the OEM photo and M16x1.5 to -6AN adapter example I included here] and some have the o-ring at the collar/neck. So, I'm not sure I've got the terminology "metric o-ring port" entirely correct, but again do I really need o-ring flange?)
As I've thought about this more I remember why I felt I could go with the 20mm x 1.5 metric to -8 AN flare
adapters despite the OEM o-ring flange style. The OEM style engine oil cooler lines have metal end and a rubber center section. What follows is my logic and purely conjecture and not all terminology may be technically correct. In order to form a seal with the metal tube at the radiator end of the line GM chose a o-ring and compression flange on the metal tube itself. That may have been easier and/or more cost effective than trying to form a seal between the metal tube end and the M20x1.5 nut. And furthermore this design forms a type of swivel end; directly threading the metal tube end would have required spinning the whole cooler line to thread the end into the female port on the radiator; impractical. So, whereas I don't need to seal a separate
internal metal tube to the radiator port (as in the OEM design), I felt I could use the 20mm x 1.5 metric to -8 AN flare and seal the threads instead (my entire hose assembly is listed in the original post; and, on this login, I'm going to go ahead and finish putting the custom hoses together and install them).