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Hello I’m I need of a bit of help as my 76 corvette failed smog. It failed because of high HC and NOX emissions it also failed a part of the visual inspection because its “missing the evap canister” even though it is there. What can I do to lower the emission and what do I do about the technician saying It’s missing? Here is the chart I got if that helps any.
Order the 76 AIM from one of the supporting vendors. That way you can show the guy where it is. It'll do you good to have it also. If he is your typical smog guy he won't know crap about a 1976 Corvette so you're going to have to point things out.
Change the plugs, the oil, ensure your air filter is clean, and make sure your timing is set properly to pass. Ensure the car is all warmed up prior to showing up for the smog test.
You can ask them for a pre-check prior to real smog test too.
Did the smog guy tell you anything about what he thought may be the cause of failure?
Originally Posted by Joshua Ruiz
Hello I’m I need of a bit of help as my 76 corvette failed smog. It failed because of high HC and NOX emissions it also failed a part of the visual inspection because its “missing the evap canister” even though it is there. What can I do to lower the emission and what do I do about the technician saying It’s missing? Here is the chart I got if that helps any.
Last edited by carriljc; Dec 28, 2020 at 09:31 PM.
I would imagine you paid for this test., take it back and ask for it to be done by a component person
He should know where or how to find the canister.
Back of the ignition timing , that will bring the NOx down , change the air filter as well that will help.
check and make sure you have no restrictions in the exhaust. damaged pipe/ mufflers etc
good luck
Turning the idle mix screws in until you get a 50-100rpm drop will get you as lean as possible at idle. Max power is with timing set for 34degrees, but if you retard it back to what the sticker under the hood indicates, it heats up the exhaust and burns off more. (Credit to Lars)
I recently needed a new coil, and put in a news ignition module as well. Instructions said plugs could handle up to .050 gap with the higher power coil. I’ve heard the high resistance from such a wide gap is hard on the rest of the ignition, but I’m theorizing it might help temporarily with passing smog tests; I’ll try it next year. It used to take two tries to pass. Lately, I usually pass on the first run. Lucked-out on the last test; the tester looked in the wrong column on his chart and passed me with the ‘no cats’ category.
Charlie
as far as the "canister, fuel vapor" you can also show him some pictures from our vendors where they point out where the "canister, fuel vapor"....is located.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Joshua Ruiz
Hello I’m I need of a bit of help as my 76 corvette failed smog. It failed because of high HC and NOX emissions
High HC is a sign of incorrect ignition timing. Your timing is too far advanced. Make sure you have the initial timing down in the 6-8 degree range, and make sure your vacuum advance is hooked up to ported vacuum and not to manifold vacuum.
High NOX indicates that your EGR is not hooked up or functioning. Fix your EGR systems and the vacuum operating system for the EGR.
If someone has disabled your emissions hoses and systems, you need to fix them. Put the car back to its original condition and tuning specs and it will pass just fine.
Lars
Smog test failed
