SU Needle Myth?

[nismou20]

So many years ago I read that N17 were Smog needles and that N25 were non smog. Is this a myth? If in fact N25 is a smog free needle I’ve never seen a part number. Does anyone out there have definitive info on where N25 came into existence? Does any other Datsun come stock with this needle. Just curious. Dean?

[bobd]

https://www.ztherapy.com/


Master TuneUp kit includes: 2 nozzles w/fuel line, new RA or N25 needles, new needle & seats (float valves), new float gaskets, "Just SU's" DVD, insulator gaskets (4) Core is $100.00 for the pair of nozzles. Send us your old nozzles for $100 refund.

[JT68]

Going from memory, I think that's backwards on the needles, the N-17 being the earlier, the N-25/27 being the later with emissions and probably leaner. The N-25 was definitely a Nissan part, but is NLA.

Being near sea level, we generally find the N-17 preferable. It is probably a bit rich at altitude.

[70MTRoadster]

I'm at 4,684 ft. with stock SU U20. What needles would you guys recommend?