I finally have my car running and all is good, except emissions . New 350 gmpp crate deluxe, 600 holley 4160,new magnaflow cat. All new filters, plugs, wires,and distributor. fresh oil change. went up to get the "sniffer" treatment and it went as follows:
25 mph test
reading allowable
hc 0071 168 max PASS
co 05.46 2.11 max FAIL
nox 0180 1208 max PASS
co-co2 11.9 6.0 min


15 mph test

hc 0084 173 max PASS
co 05.58 1.63 max FAIL
nox 0155 1323 max PASS
co-co2 11.8 6.0 min

I do have an EGR valve but discovered when I got home that it is not working (will replace). I also noticed my fuel pressure was 9 psi (turned it down to 6) my timing was set @ 2 degrees btdc (for emissions)
Carb floats are set till fuel seeps out holes when you gently shake the car, choke is operational (open fully when warm) Idle mix screws turned out till highest rpm then in 1/2 turn. No stumbles or bogs. Starts right up cold. Is tempermental to start when hot??? Have to pump gas several times to get to start. (not a cranking problem due to cvr mini)
Have in the past used denatured alcohol in the tank. Would rather not unless I have to. I dont remember if alcohol helps with co levels anyways? Any help would be greatly appreciated. I did a search but the results seem to be taylored to what the individual's levels are.

 

help

 

I've been dueling with the emissions stuff here the last couple years as well. You have the Vortec headed 330hp 350 HO right? Very similar to what I'm running.

Previously with extra high CO like that I've changed my cat and then gone in and passed. Last year it wouldn't pass even with a fairly new cat (which you have as well so you're good there).

What I ended up doing was lowering the timing, cutting down around 3-4 sizes on the jets (Holley 750), and lowering the float level well down below the sight hole. This made the car drive like crap, with a wicked lean stumble at light throttle that you would think would be bad for emissions. But I limped it down to the test station, and it blew numbers so low on both the 15 and 25 tests that you'd think it was coasting... Drive her home and tune it back to normal, presto changeo back to good running and gross polluter status...

I would try really leaning her out and see how it goes... I don't remember the exact numbers mine came out with all leaned out, but the limits in my state were stricter than what you've got posted if my memory isn't failing me, so you oughta be able to tune it to pass... And I should mention mine passed with no EGR setup whatsoever...

Also do what you can to get the temp up around 200-220 or so degrees if it doesn't run there normally, I just left my fans off until pulling up on the rollers so it was nice and hot...

Good luck, I can't stand this eco-**** crap...

 

Thanks for the reply. Yes I have the vortec heads. I tried leaning it way out today but if i do by much i get a stumble/backfire when i get on the throttle much at all. Guess I could tune and limp up there then come home and retune. I am hoping to not have to get into the jetting but will if necesary.
Do you think the fuel press being @ 9 or 10 could cause my problem? I also plan on turning the timing back a little more, seemed to help in years past with the old 305 I had. I will also try the float level adjust. Thanks for the input

 

'82,,,
Other than (the obvious) 'lean it out',,,,
.
make sure ignition is as good as possible
.
make sure AIR pump is dumping as much air into the (upstream of the)
cats as possible

 

passed today :lala: :lala: :lala: :lala:
Leaned the carb out/adjusted fuel pressure to 5 psi /new egr valve/timing set a little low and just squeaked by.
contactpatch: car hasnt had air pump on it for quite some time and always got it thru in the past.......next year though i might need it to get it thru we will see. 25 years and older and I wont have to worry about it. Cant wait