I have an 1986 K5 that came with a 305. There is no diagram sticker on the radiator support. I noticed in the manual that there are a few versions for the year. How do I find out which setup I have? There were options like high altitude, Cali, and alternate.

Thanks
pt

 

IIRC it's pretty much Federal emissions for everything except California and Colorado.

If it has NA5 listed in the RPO codes on sticker in glove box, then it has "federal emissions". I suppose it could be NA1 but don't remember ever seeing that one.

Looks like California had a closed loop system with an ECM that year, but the others did not.

I found this as generic Chevy RPO codes - I believe three of them apply to your Blazer:
Can't verify accuracy for all but didn't find any conflicts either.
NA1 : EMISSION SYSTEM, GVW, LESS THAN 8500 LB
NA2 : EMISSION SYSTEM, GERMANY
NA4 : EMISSION SYSTEM, GVW, ABOVE 8500 LB
NA5 : EMISSION SYSTEM, FEDERAL, TIER O
NA6 : EMISSION SYSTEM, HIGH ALTITUDE REQUIREMENTS
NA9 : EVAPORATIVE SYSTEM, EMISSION
NB1 : EMISSION SYSTEM, CLOSED LOOP
NB2 : EMISSION SYSTEM , CALIFORNIA , TIER O
NB3 : EMISSION SYSTEM, ABOVE 10000

 

this sticker?

 

Yep, that's the one. But doesn't seem to have the RPO for the emissions. So looks like I told you wrong! Must be only listed with emissions on the newer ones. Sorry! Maybe you could take vin# to the dealer and they could tell.