AC Tach Part #'s -What are these?

[Paul_S]

Can anyone find these part numbers for AC tachometers to give me a little info on them:

#NSM5657404
#5657823 (I'm sure that's an 8)

They are both 12v universal units. I would like to know if they have a specific ignition application.

Thanks, Paul

[Mr70]

I think #5657404 is a smallblock tach for 1971-72 Malibu-Elcamino-Monte C. all w/307cid & 350cid,..And 1971 Monte C. w/350cid & 400cid w/2bbl.
#5657823 is for a 1973-4 Pontiac,maybe Aspen or similar Buick-Olds bodystyles.

[Paul_S]

Thanks Rick, but these tachs are in a housing with a lens and bezel (universal). -not meant for a factory gauge cluster. I noticed this one on ebay that looks just like the #5657823 I have but with a different needle. ebay AC Tach The 5657404 is a 8k tach and I believe is cal'd for a 6cyl. My problem is, the '404 works fine off of a clean/generated signal but on the car it reads high (points setup). Every other tach I have reads fine off of the car except the one I want to use and I cannot find a faulty component on it's board. The boards between these two tachs are very similar but I wondered if for some reason the '404 may be for a different ignition system (points triggered TI system...) or something. It looks like I may just put the car back together without it for now.