I just acquired a '73 duster w/ a slant 6. (My mom had a '63 Dart with a slant 6 when I was a young kid.) The vehicle was previously registered in an area not subject to emissions testing. I'm trying to get to pass the emissions testing program in Maricopa County, AZ.
I failed the initial test due to carbon monoxide (CO) under load. It easily passed both idle tests as well as gas cap and HC under load. It failed the CO under load test by almost 50%.
I think that this would indicate a rich fuel mixture with a partially opened throttle. I replaced the air filter, PCV valve, breather filter, oil, and oil filter. I'll try to check the ignition timing, but I think it will also need the air/fuel mixture adjusted. I suspect, although I'm really just guessing, that it would be the float adjustment that needs to be set lower. The previous owner said that he had the carburetor adjusted for Flagstaff, AZ... higher & much colder climate than where I'm at now. The carburetor is a Holley 1920. I'm not very knowledgable about or experienced with carburetors but I'd rather tinker with it myself a little before giving up and taking it to a professional mechanic.
The only suggestion I've gotten is "pour some isopropyl alcohol in the gas tank." I think that might help reduce CO a bit, but I think I'd like to try to get it adjusted correctly before I try that. We do have oxygenated fuel in Arizona in the winter only(Ethanol is added) to reduce CO emissions but I'm not sure when they're switching it over. Can someone tell me how to adjust the float level?
I'm enjoying the site and the messageboard. Any help, suggestions, advice, reccomendations for mechanics in the Phoenix/East Valley area, or even just words of encouragement will be greatly appreciated.
Thanks
TheFatWorm

Howdy neighbor. Welcome to the board. High CO indicates incomplete combustion which can be caused by a number of conditions. There are guys here who can diagnose it far better than I can, but I would start with a complete and careful rebuild of the carburetor and check the jet sizes. If it was leaned out to run well at over 7,000 feet in Flagstaff you could be getting a lean misfire down here in the valley. Be sure to check the throttle shaft for excessive side play and possible air leaks as well. Vacuum leaks and faulty carb components as well as ignition problems can contribute to it too.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Thanks for the reply,

I'll change out the spark plugs and check ignition timing .. I didn't really check those yet because I was kind of assuming it was fuel related.

Complete Carburetor rebuild.. I was hoping that wasn't necessary and it sounds pretty complicated/difficult... not sure if I want to tackle that one myself. It might be beyond my skills/abilities. Know anyone that specializes in carburetors/emissions?

I did a visual inspection of the vacuum hoses and don't see any that are cracked/leaking.... is there a better way to check that?

Could you explain more about the throttle shaft? what/where is it?

Thanks For The Help

TheFatWorm

I thought someone else might chime in here. The throttle shaft it the rod to which the throttle butterflys attach. It runs through the base of the carb and has the throttle linkage at one end. Over the years it can wear and loosen up so that air can leak past it into the throat of the carburetor. Spray some WD40 onto the shaft while the engine is running. If the speed of the engine changes then the throttle shaft is leaking air and should be rebushed to tighten it up. The WD40 trick can also be used arounf the mating surfaces of the intake manifold to look for vacuum leaks there. Whatever you do, resist the temptation to buy a "remanufactured" carb from a parts store; those are trouble in a box. There is at least one carburetor rebuilder in the Phoenix area and maybe more. I would find them and talk to them about your car.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

It sounds like your car runs pretty good, and that tells me that the carb my be in fair condition anyway and setting the float is probably not going to help. Although a rebuild may still help abit, but I think tuning will help you out the most. Have you even tried to ajust the fuel mixture, this can make a diff.


But with the trouble you are having I think there is some other things you can do to get this to pass. Yes the ignition has alot to do with emmisions. First read up on the Distributor & timing, It would help to recurve the Dizzy(ditributor). If you feel this is more than you can do then atleast make sure the vacume advance is working good. Your timing chain is probably getting a little wear on it & so some advance on the timing at the very least will be needed. Then try to advance your timing up as much as the motor can take without pinging or spark knock. Also put premium fuel in it when doing this & it will allow you to get more advance. this will help it clean up the exhaust under a load. Also look unto some of the threads about spark plugs on the forum, the right set with the right gap will help it run better & cleaner. Does this car have pionts ignition or electronic, if it does not have electronic it could help to change this over, it will run alot better. Putting a bigger coil that was made for more spark can help this out also. You can get one at Autozone or advance for not to much money, the Accel yellow coil works good(not the supper coil but the one that is shaped like the factory coil) or you can go to the junkyards and get one off a import car that will put out more spark ( I use to use the ones off the mid 80s Nisssans) they are noticably bigger and put out a lot of spark.


Also ajust the rocker arms or valves, this can also help. Do the valve ajustment before doing anything. It is very possible your engine needs a little freshening up, atleast a good valve job but you may get by without it. Still my guess is it could help the engine run a lot better. But if you ajust the valves & go over the ignition as I discribed I believe you can get to where you pass the test.

If your running the factory air cleaner then a taller element could help also, this will give it more air and could even effect the carb in a way that it doesnt give as much gas to the engine.

There is other things you can do if this doesnt get your test passed.


Jess

No technical help sorry,
but
I am surprised - a 73 anything has to pass an emissions test?? They don't have a 20 yr old or historic vehicle exemption?

I mean to what standards do they expect a 73 to meet?
seems a little ridiculous!
I think even the People's Republic of California exempts cars over 20 yrs from SMOG.

75 and older are exempt (and diesel and motorcycle)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The first engine exhaust emission control standards were in the 1966 model year in California, 1968 for the other 49 states. There are many locations where even very old cars have to pass emission tests before being allowed on the road. The standards are appropriate to the age of the car—they do not require that a 1973 car be as clean as a 1983, 1993, or 2003 car. And in all cases, the standards for old cars are ridiculously lax, such that the car would have to be a truly gross polluter to flunk them, in which case the car wouldn't belong on the roads anyhow.
Not for those of us who like to breathe, and who like to drive old cars responsibly. The stinkers give us all a bad name.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Arizona has an exemption, just passed and in the implementation process, for cars 25 years or more old provided they have valid "collector car" insurance. Those policies generally preclude regular daily use so will be of little benefit to someone who wants to use an old car as a daily driver. Here they have to pass the test to the standards in effect at the date of manufacture. Technically they are supposed to have the factory emissions equipment installed and functioning but as a practical matter I don't believe they follow that closely if the tailpipe test is good. The tests only apply to residents of a couple of counties, mainly the greater Phoenix area, but they do include deisle vehicles and motorcycles.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Washington State exempts all vehicles older than 20 years. Although I don't encourage disabling the emissiosn devices. Nowadays you can get high-flow cats so there is no point to dump them (especially since you can't buy regular anymore). I still don't run EGR valves though. But all other emissions devices (except the OSAC) should stay.

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Casually looking for a Clifford hyperpak intake for cheap.

I kinda wish the car lobby would do a write in campaign to Oregon, our DEQ quotes the fact that they have had clean air in Portland since the 1980's (I wonder why it's brown most days.... )....is the fact they instituted mandatory testing for all 1975+ vehicles....

They go as far to say that there are fewer pre-1975 vehicles on the road that they don't add to the smog factor (but oddly 31 years later there must still be the same amount of 1975-1981 vehicles on the road as there were in 1985, causing the smog...)

I wish we could write in and have it voted to have a 20-25 year rolling exemption....oddly due to this funny little law, Salem,OR per DEQ has over 1.5 million vehicles registered in the city limits (we have a population of about 150,000....so I'm still trying to find the other 8 cars I should own on the average that someone in Multnomah county is driving!!!!)



jeez...

-D.Idiot

I passed!

I gave up on adjusting the carb and just went ahead and tried again with new spark plugs, distributor cap & rotor, ignition wires, pcv valve, breather filter, air filter, as well as fresh oil, oil filter, and a bottle of HEET(not sure how much this helped) in 1/2 tank 87 octane gas. I was going to adjust the ignition timing but my light is dead anyway before I got 5.89%, this time 2.33% (the loaded standard for this vehicle was 3.75% CO)

Thanks to everyone for your help.

I agree that testing '73s is a little ridiculous Mr. Belvedere, It doesn't even have a cat! How many cars that old can there be left on the road anyway?

I don't think emissions testing is effective anyway.... too many people cheat(register out of area, alcohol in the gas , small exhaust "leaks" ----in my 93 corolla when a had a big gaping crack in my exhaust manifold I always passed "with flying colors" as they would say.... when I fixed it and put a header on It failed the NOX test(NO EGR VALVE --I thought just about all cars had one but this one doesn't) and had significantly higher emissions test readings in other categories) (IT passed on the second try) plenty of folks figure out easy ways to beat the test, problem cars aren't always easy to fix, many people change the settings for the test and then change them back immediately afterward, having such widely varied standards for different age and TYPES of cars/trucks seems a bit unfair to me, they never account for how much the car is driven, and even well running cars have to go through the inconvenience and create pollution waiting in line... It might even be counterproductive. The air is getting cleaner... but I don't think it's because of emissions testing. We still do have problems with pollution here in the valley of the sun but I don't think emissions testing is an effective solution.

I saw an old widow in the testing station after I failed and she claimed that she spent $1600 to get a new cat put on her '95 car to try to get it to pass and it still failed. People don't know what to do to get their cars to pass and lots of these "mechanics" are Jackals who will try to take advantage.


I think it will take the EPA about 2 years to approve the new emissions test law for collector cars in AZ that got passed! but I can't afford to have a car that I can't drive anyway. I think a 25 yr exemption might also be in the works,(under consideration in the legislature) but will of course probably take at least another 4-5 years to implement IF we can get that!

The problem is that any change to the emissions law requires EPA approval and they demand extensive documentation, implementation plans and contingency plans. Even if the law is passed, and this goes for Oregon too, it will take years for it to get implemented if it ever does. In Oregon you've got so many green weenies, especially in Multnomah and Lane counties, it's unlikely to pass anyway. That's why they still have a 65 mph speed limit on the rural freeways.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Oh, before I forget, congrats on passing the test.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.