Arizona emissions testing HELP

Can anybody give me some tips to passing Arizona's I/M 240 emissions testing. I have a 74 Ford F-100 4X4, 360 converted to 390, with an aftermarket Q-jet carb with Edlebrack intake manifold. The conventional ignition was converted to a late 70's Ford electronic system. The carb has been de-jetted to the point I don't think I can get smaller jets. The rebuilt engine has apx 40-50,000 miles of use. Over all it runs great, the problem is with the Co. I need to lower it just a bit to pass. I cheated last year, getting by on the re-test by going through in 4 wheel low. This year the inspector was wise, moved it back into 2wl high and I failed on the high speed test.

Any suggestions are appreciated. I just need to get the Co level down just slightly to pass. I would really like to get it through legitimately without red-lining the engine in 4wl low. A local garage lowered the Co levels once by changing the park plug gap. Unfortunately I can't recall if he increased or decreased the gap. I've heard various gasoline additives will lower the Co levels a bit, but I don't really know if I'm relying on sound advice or an urban legend.

Reply to
Jim
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I'm no expert, but I thought that spark had nothing to do with CO but only with HC. I know that some garages try to fix any emission problem with a tune-up, even if it won't help at all.

Also I don't understand why your truck has to pass the IM 240 or IM

147 test because that applies only to 1981-1995 vehicles, and the test your truck needs to pass is done at idle and at 25 MPH:

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The AZ auto emissions lab, which used to be around McDowell & 36 St., can be very helpful, and they'll even test vehicles and suggest fairly specific remedies.

Mark Salem also has some emissions info:

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He hosts an auto program in Phoenix on KTAR 92.3 FM (also webcast) every Saturday from 11AM - 12PM and answers e-mail. You should probably post all the emission test results (HC, CO, CO2, NOx at each speed), both to him and in the newsgroup.

I've read that if a carbureted vehicle has low CO at idle but high CO at cruise, then the problem may be the power pump or metering rod system.

Reply to
larry moe 'n curly

Thx for the responce and my apologies about the IM 240, shows how little I know about the testing.

Reply to
Jim

Post the full results of the test and there is a good chance we can offer some suggestions to help you pass.

Based on the limited information in your original post I can tell you that high-speed CO failures would seem to implicate your high-speed (i.e. main ) circuit. Either main jet too large or air correction jet too small.

Chris

Reply to
Hal

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