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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Creedsmyname on August 02, 2014, 01:50:56 am
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So I've been trying to get my truck to pass emissions for quite some time now. It's a 76 k10. Rebuilt engine and carburetor, edelbrock. So I've already had it tuned up and re-timed to try and get my CO levels down. It was timed way off so I had it dialed back to manufacture settings. The problem is that my CO at 2500 RPM is at 8% and it needs to be below 6%. That is the only thing that has not passed. I do not have any cats on my dual exhaust, and I would prefer to keep it that way. It was suggested by the performance shop that my carbs be re-jet. But me and the shop both agree that we would like not to rob the truck off all of its power while we are doing this. Wondering if any of you have any suggestions.
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The question that needs to be answered first is, can your carb. be tuned the way it is so it will pass the 2500 rpm test, and still pass any other test's. Or is the 2500 rpm test the only one they do ?
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You need to provide more than your CO results.
CO - O2 - CO2 - HC - NOx should be displayed on your test results.
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Everyone of my other tests passed with flying colors after having it tuned up. They said it can't really be timed down or tuned anymore to get the numbers down. It passed all tests at idle, and only failed CO's at 2500 rpm. I was just looking for alternatives to adding a cat, or rejecting the carb to smaller jets. I don't want to gut the power to the truck.
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Re-jetting*
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The various gas concentrations are intimately related and necessary to provide a complete picture. Withholding quantitative data from your test effectively blindfolds us. If you're serious about wanting options you should answer Vile's question....
You need to provide more than your CO results.
CO - O2 - CO2 - HC - NOx should be displayed on your test results.
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Since you're close I'd try retarding the timing a bit and higher octane gas. If you have the ethanol crap in the gas in your area. I'd try using pure gas.
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By providing the numbers from the rest of the tests they will be able to determine what exactly can be done to pass the 2500 rpm test. Re jetting a carb or a timing adjustment isnt always the answer to make it burn clean