1973 L-82 4spd stock with the exception of MSD electronic ignition, Edelbrock 2101 performance intake and Edelbrock 1406 600cfm carburetor. Smog pump was removed by previous owner. In Delaware must pass emissions for an antique vehicle. Limits for curb idle hydrocarbons 600. Failed with a 2748 reading. Any ideas to get vehicle passed? Thank you in advance for advice. John H. Parker jr

 

Found a bunch of stuff. Happy reading:https://www.google.com/search?q=how+...h=468&dpr=1.82

 

The above post has a lot of good info.
in short, you need to make your engine run worse.
retard the timing a lot.
lean out the idle mixture as much as you can

 

Pay someone to look the other way and put a sticker on it.

 

It may be soon that all this emissions crap will get rolled back. California just got their stupid CARB regulations pretty much knocked out.

 

I would find a small catalytic converter that would fit under your Corvette in the exhaust system! Catalytic converters DO work and they are getting cheaper. They don't need anything but heat from your exhaust to make them work. I bought a replacement for my 1988 and was surprised at the various options available, the new converter was much more powerful than the original and has worked for years. Call Summit Racing and tell them your issues, they might be able to help you. I would install a converter and then remove it if you don't like the effects it has on the Corvette. I suspect you would never know it was there, performance wise.

Have you taken your Corvette to have a mechanic using a exhaust gas analyzer to help them lean out your carburetor as much as is physically possible? Clean Oil is a Must for passing an emissions test if you are on-the-line. Good Fresh Ethanol laden fuel might help your numbers. (I NEVER thought I would suggest somebody use the Ethanol mixture they call gasoline). How about the timing, It has to be accurate and set correctly for clean exhaust. Clean air filters are also helpful. I would do a good tune up before testing it again. A powerful ignition COIL could help burn some of those hydrocarbons as would some new spark plugs. You want the ignition system to be working its very best to get through the test. One miss, every so often and your numbers will go shooting up so even spark plug wires can affect your test results. You want the car to idle smoothly and NO holes in the exhaust that can suck in extra air which affects the final outcome of the emissions testing.

Here in Virginia they are tougher on some of the older vehicles. They now check for the emissions equipment that was installed on my engine in October of 1967. My car has the smog Air pump and a PCV and that was all there was. They last inspector asked about my air pump and then laughed, I was so relieved. I have been told that performing a good tune up prior to getting the test done is one place that really helps, this is from my mechanic.

Also having a 1988 C4 I have had issues with my emissions. My car failed an emissions test and it was all because of the EGR having failed and making tons of pollutants and a high level of Nox. I replaced the EGR system and all is great again. I have a Cat-back chambered exhaust system that is connected to my catalytic converter, the exhaust sales people suggested I drop the catalytic and put in a test pipe in place. I am glad I did not follow their advice because they look for the catalytic converter under the vehicle.

The end result of passing the emissions test is possible with a great tune-up and good gasoline and fresh oil. If you still have trouble then I would consider putting a catalytic converter in the exhaust system if it is a single exhaust or possibly 2 catalytic converters on a dual exhaust system.

I wish you the very best in getting your car on the road again. Just a slight delay and off you go. Here in Virginia they have a specific amount like $600 that you can spend on the work of getting correct emissions past on a vehicle before they sell you an exemption. From that point the emissions test is no longer required.

 

The land of Washington , Henry and Jefferson has lost its way even more than when I left in 95. So glad to be in Florida. If we could just get a few more from up north to move back but that's the attraction of Freedom.

 

In general terms, High HC is a timing problem. High CO is carb. Get your timing retarded to no more than the "sticker" spec, which is probably around 6-8 degrees. Make sure you are not running manifold vacuum connection on the carb for your vacuum advance - you need to run ported vacuum so you have no vacuum advance at idle. Then, lean it out per the Service manual instructions with a 50 rpm lean-drop idle mixture setting. That old Carter AFB carb you're running is not a good emissions carb - one of the reasons GM discontinued its use after 1966. You stand a better chance of passing the test with a 1973 Q-Jet. With the 2101 manifold, I assume you have deleted the 1973-required EGR and that you are also not in "visual compliance" on the emissions system..? And you're also probably missing the A.I.R. system..?

 

I would add that the engine running temp should be around 200-210, at a minimum, not too low, 175-180, and not excessively high, above 230+. Higher cylinder heat temps will help burn off emissions, up to a point.

 

Exactly, and this is the reasdon for running the retarded timing - it will produce those higher cylinder temps and will lower emissions.