Its that time of year again....

After my 5th failed emission test I've just about had enough. i am looking to do this the right way, but am running out of patience trying to get through.

Heres the scoop.

383 stroker motor <1500 miles
Normal timing is 16*
edelbrock 1806 carb.
edlebrock cam (specs I dont remember at the moment)
Idle @ 1000 RPM
Smog hooker headers, A.I.R pump, magnaflow oversized converter

first test was failed on all 4 tests

Loaded HC 228 (220 allowed) Idle HC 330 (220 Allowed)
Loaded CO 5.23 (1.2 allowed) Idle CO (7.21 1.20 allowed)

the latest failed test;

Timing 4*
3 steps lean on rod in carb
Idle mixture screws nearly closed
Idle 1500 RPM

Loaded HC 11 (220) allowed Idle HC 47 (220 allowed)
Loaded CO 0.01 (1.2 allowed) Idle CO 4.27 (1.2 allowed)

The other tests are close to this last test in regards to numbers, test number four had around 6* timing and the Idle CO was 2.07, thus the closest to passing. I thought retarding it more and leaning it out, and increasing idle speed would get me over the hump...it did except for that idle CO. What else am I missing here? I passed last year with similar setups, however I blew a collector gasket on the dyno and thought that may have helped me pass....With the discrepency in loaded and idle CO, its apparent its a cam selection issue. Any thoughts or suggestions?

 

Timing primarily affects your HC, so retarding it helped there. High CO, as you know, is from a rich air/fuel mix. Is your air filter good and clean? A dirty filter will raise your CO readings, whereas a better flowing, less restrictive air filter can help lower it. For the next test, you might want to make a quick pit stop right before getting to the testing station, and remove the filter element altogether (if still using the stock air cleaner). If you have an aftermarket, open filament air cleaner, rip out the paper portion and just run with the wire mesh for the test. It doesn't get much less restrictive than that. Which kind of air filter are you running with?

 

That is the bad thing about some aftermaket cams sometimes you just can not get them to pass. When I did testing is West Chester PA there was a $250 limit the customer had to spend to get their cars to pass. After that we put a sticker on. Even with a fully adjustable Holley and the machine hooked up in real time some of the more radical cammed cars just would not pass.

 

69: it is an open element type. I will try removing it for the next test, as they don't open the hood now that I've passed all the equipment inspections.

Gorn: AZ has a one time waiver after x amount of dollars are spent, however once the waiver is used it cannot be used again. It is very obvious EPA, and the states do not want these cars on the road, but there are many hot rod guys out here who get them through, so I don't see why I cant.

 

You can try to raise the cylinder tempture. A 195 Thermosate and some hotter plugs. I have not worked on the elderbroc but is sound like you need to drop the fuel level in the bowl. This should have some effect on the loaded CO. After that the only thing left is to re-jet the carb.

How is the load test preformed? Is it a light load? If they are getting on it hard the above ajustment can cause it to spark knock and the will throw everything out of wack.

I never dug into it deep but I alway assume the cars we could not get to pass had a lot of valve overlap. If you have that there is not much you can do besides a air injected Cat. Cams with a lot of valve overlap are nomally Turbo or Supercharger cams.

 

The coolant temp is right around 190 while on the dyno, I would believe cylinder temp is similar. The loaded test is done by me "driving" the car on a dyno @ 31-35 MPH with a probe in the exhaust. The idle test is done in park with a probe. Loaded hasn't been the problem, its just the idle CO test. I will check float level again, I can't imagine its a jetting issue because above idle everything checks out.....I am leary of changing plugs out only because the jetting seems good to lean above idle and i am concerned about running a hotter plug. I once put a hole in the piston one of my race bikes playing around with jetting (before FI on dirt bikes) and found while fat on the bottom, it was lean everywhere else.....which was correct for that application.

 

As far as the cam is concerned, more overlap will affects the HC readings. You're real good there, so I wouldn't be looking at the cam as the problem. Another thing you can try, in addition to the air cleaner, is this stuff: