Emissions and timing question

[77Mule]

I have a 77 with stock 302, dual exhaust, rebuilt 2bbl carb, new plugs, wires, cap and rotor. the cataletic converter has been removed. Stock cam as far as I can tell.

I did not pass my Missouri emmissions test. It failed for too high of CO(Carbon Monoxide) content: however the HC (Hydro Carbons) were acceptable.

The factory timing should be 8deg BTDC.

Any ideas of what to detime it to to get it to pass emmissions easier ?

How do I lean out the Carb also to maybe help?

Do I lean out the carb and then detime it or visa versa ?

Thanks

 

[bert]

Everything you mentioned will affect emmisions.
If it has been a while since the last oil change, change it first. Get engine to operating temp and set ignition timing. Adjust carb mixture to obtain lean best idle (mixture screws in front of carb). Make sure choke is fully off. If you have an EGR vavle, make sure it is not leaking. Make sure you are not pulling fuel or fumes from the canister vent at idle.
Rebuilt carbs (from parts stores) are not always exact replacements. They may have a higher float level than needed or jets that are too large.
What test does your state run? Two speed? (Idle and cruise). If they gave you a print out of your test results, does it show O2 and CO2? These two gasses are better for diagnosis than HC or CO.

 

[BwoncoHowie]

Sounds like it's running too rich. If adjusting the screws doesn't work, you could have a leaky power-valve, or the float level is too high. I don't think retarding the timing will help your CO very much but the most you should go is 3*deg., which will put you @ 5* deg BTDC in order to remain within passing timing specs.

If the carburetor checks out to be ok, you might be looking at throwing a cat back on it especially if the air pump has been removed.

They don't issue certifications here in CA if any emission control device is non functioning or missing regardless of how clean the sniff test is. I feel your pain, hope you get it worked out. ~BH

 

[YellowBronc]

Missouri emissions test???????

I haven't had any emission test on any of my vehicles in the 10 years I've lived here. Is this just a St. Louis regulation???

 

[77Mule]

Missouri emissions test???????

I haven't had any emission test on any of my vehicles in the 10 years I've lived here. Is this just a St. Louis regulation???

Just wait it's probably coming my Bronco brother. We've had them in St. Louis forever, especially if you don't get Historic plates.