1981 K20 emission questions/thoughts

[Biggyniner]

Hi Everyone!

My father gave me my first vehicle, our 1981 K20 with 70K original miles (heavy duty M vin), all original except for dual flowmaster exhaust.  She runs and drives great!  I am in the process of restoring the interior and all the door/window seals.  One thing that has always made me sad is the whopping 160HP this thing produces, I mean my 92 Jeep XJ has more power...  Anyway I have always wanted to build the engine and make it produce actual V8 power.

As many of you know this model had no cats from the factory - really all it has is the AIR pump and EGR for smog (and of course carb detuning from the factory).   I would like to put vortec heads on, crane timing advance, keep the q jet carb, eldebrock intake, Comp smog legal cam, and throw headers on it.  This means removing the AIR pump and possibly the EGR.... My question is if I do this work but make sure the engine is tuned well and running good do you all think it will pass smog?  Here in Oregon all we have is a sniff test - the only visual they do is for cats and I don't need those...

Thanks for any advice/opinions...

[Captkaos]

If built properly it should pass smog.

[Biggyniner]

I thought as much - and i actually may run the Comp Cams X4254H 4x4 cam instead.  Little more aggressive but still not so crazy that I hope it won't affect smog too greatly..

[nazielinski]

In my opinion q jets are junk carbs and have alot of problems i would go with a 650 holley or demon

sent from my fingers

[Captkaos]

In my experience squarebore carbs (Holleys and Demons) are good for Race settings only.  For a driver you can't beat a q-jet, plus it will have smaller primaries unlike the other two giving you the ability to cruise on smaller venturis.

[Irish_Alley]

if you had a company that made good carbs (quadrajet) for 25 years (from 1965 to 1990) and you put them on most of your vehicles. then 30 years down the road that carb needs a rebuild. this would be a good time for another company to start selling wives tales about how much better their carbs are. cause if you just rebuild the Quad and be good for another 20 plus years that 2nd carb company wouldnt make any money.

now like Capt said different applications may require a better flowing carb. but for a stock 350 a 550 cfm carb is big enough and Quadrajets are made for that job (up to 800 cfms) and to let you keep your mpgs

[VileZambonie]

In my opinion q jets are junk carbs and have alot of problems i would go with a 650 holley or demon

sent from my fingers

I couldn't disagree more with this. You can get great results out of a Q-Jet and less problems than with Holley. Holley's are way too static while Q-jets give you a much more dynamic range of performance and operation. Of course it's all dated technology anyway, EFI is the way to go regardless

[Dr_Snooz]

I'd keep the EGR. It helps prevent pinging. As for the AIR pump, I'm not convinced it ever did anything useful. And it looks like an ugly parasite perched on top of your engine.

Depending on how, and under what conditions they do the sniffer, it should pass if you have the carb tuned properly. Regardless, you should still be able to tune the carb to pass most tests. It helps to have an A/F meter. Tune as close to 14.7 A/F as you can under the test conditions and you should have no problem.

The only real danger is if they change the testing around (like CA keeps doing) and introduce a visual test in the future. It could leave you unable to renew your registration.

[Irish_Alley]

in delaware i had to pass visual and the sniffer. probably not as strict as CA. but it took me a couple times to pass but all i had was the Cat. and egr. i took the egr off once i passed due to in my logic ir replaces unburnt dirty air/fuel into your engine when you could be burning fresh air and fuel for more power. did it make a big difference in power? probably not

[Dr_Snooz]

I'm with you Irish. It doesn't make much sense. EGR is supposed to "cool" the combustion burn by recirculating exhaust gas back into the combustion chamber. Yet the exhaust gases are the hottest part of the burn by far! No one has yet explained that to me in a way that makes sense. At any rate, EGR is supposed to help prevent pinging. Whether it really does? Who knows.

[VileZambonie]

Simplified explanation for you: Inert/spent exhaust gasses cannot increase the temperature of combustion, the inert gas effectively lowers combustion temps and the result is a reduction in oxides of nitrogen. In addition it helps reduce pinging.

Primary and secondary A.I.R. is ugly for sure but it did provide functionality as well. Primary helped complete combustion of any residual HC's and secondary helped the catalyst function more efficiently.