Emissions Test - Big or Little Carb

[Terry Stapley]

Does anyone have any experience or knowledge with passing emissions on a carbureted engine?
Which is easier to tune, an 850 cfm or a 600 cfm with all other items being equal? It seems like the more air that a carb could flow the better it would be for a lower hydrocarbon count at idle but maybe the airflow at idle is the same in both carbs!
Inquiring minds want to know so please chime in!!

[strictlypersonl]

The smaller the venturi, the better the fuel atomization at low RPM. Use the 600 cfm.

[Ron61]

Normally I would say the 600 also, but some will depend on how they do your emission testing. Here they do the idle and at different RPM ranges plus the ever present visual test. If you have the wrong carb on, no matter if it passes the sniffer test they will fail it. And the visual includes replicas. I know of one person who registered his by the year of the engine as he couldn't get a SB-100 number and it passed the sniffer but he had the wrong air cleaner on so they failed it. All in the interest of money as a chrome air cleaner won't pollute any more than a painted one. But they got to charge him another $100 for having to put the painted one on and go to the referee.

Ron

[jwd]

Size has nothing to do with it. Both carbs. can be jetted to give the same A/F ratio.

Jim

[427 S/O]

Don't forget to unhook the PVC, it'll run a little rough so just up the idle. Let's more oxy in.

[CobraEd]

And throw some alcohol in the gas. It burns emmisions free. I used to do this to pass emissions years ago and it worked

[Ron61]

JWD,

True that both can be jetted to give the same A/F ratio, but I am going on how they do our tests here and I am guessing his engine was a 351 stroked to the 418. The 351 wouldn't have came with an 850, and they do check the number on the carb. here during the visual inspection. Maybe where he is at they don't even do a visual inspection. It does no good to jet the carb. to pass the sniffer test here if you have the wrong carb. on. And if you have the PCV unhooked they will fail you regardless of how the sniffer does. The alcohol trick has been used here with good results.

Ron

[jwd]

Point taken Ron. I'm sorry anyone has to go through the crap they do in Ca. For those in Washington that are required to be tested, it's sniffer only. They never open the hood. I'm registered as a 1965 so I guess it's a moot point.

Jim

[Ron61]

Jim,

I just can't understand what chrome air cleaners or Cobra valve covers has to do with anything. If it passes the sniffer test, it shouldn't matter what you have under the hood. I think the whole visual thing is just for money. Fortunately I had the SB-100 number when I had my car.

Ron

[Terry Stapley]

Ron, no visual test here in Utah or 2500 rpm test as there used to be! Idle test only now!!
How much alcohol can one add without affecting rubber fuel lines as I have heard that alcohol and rubber do not go together!! (No Pun Intended)

[GlynMeek]

are we talking pure ethanol when you say 'alcohol'? Where can you get it?

[RICK LAKE]

Terry Stapley The smaller carb is better if you are just under the limits. They sell a bottle of mixture that you add to a tank of fuel that will get you through emmissions test. Make sure you put a new set of sparkplugs in the motor, and change filters. The biggest thing if you go to a SI station is the waiting in line. You didn't say how big the cam is in your motor, Don't idle the car for a long time. I used to push mine through the line wait. Right before you are next start the motor and high ilde it at about 1,500 rpms to clean out the exhaust. You should go right through. Retard the timing 2-4 degrees on basic, this will help also if close to the limites. Rick L.

[patrickt]

Originally Posted by RICK LAKE

I used to push mine through the line wait.

Man, if anything would be a red-flag to me it would be Rick pushing his car up through my inspection line. I'd go over that car with a fine-toothed comb.

[vettestr]

In the ultimate wisdom of State government Arizona mandated the use of oxygenated fuels for several months per year. They chose MTBE or an Ethanol or an alky mixture with some terrible results. The MTBE was droped as it created health and contamination of ground waters etc... The alky mixture was up to 15% and had its share of issues but is still being used but with its own set of problems caused. Below is what use of alky at 15 percent proved to be true but more so with older cars and materials used in older car builds or alky compatible materials in your build. I do not know how much is gained by its use in hard fact or numbers but it must have some benefit.

Problems = A> alky is a great solvent/cleaner @ this percentage in a fuel system so when run in older cars it cut loose varnish,rust and crap from fuel lines,tank and carb killing many cars. B> a lot of rubber types used in fuel lines, pumps, gaskets and carbs were not compatible with alky killing a few more cars. C> alky is corrosive to aluminum and eats areas not anodized or with some protective coating so a few more cars had issues. D> Mileage and power went to heck with hard starting or vapor lock when hot got a few more cars. In the end it caused XX amount of cars to be killed/parked or repaired until compatible. The remainder and newer cars run on up to 15% alky but the gas cost is much higher and mileage dropped causing another cost increase but has the smog problem been helped???

[RICK LAKE]

patrickt Every year was an adventure with SI. Thank God the jeep was only 2,400 lbs. The AMX motor in it was very warm with a .550" cam. As long as the idle was in the 775-800 rpm I would pass. Anything below and I failed. The other thing is the Jeep CJ5 is a roadster. The safety chains where a pain. My side pipes where factory installed and got I letter for Jeep about they where factory and failed every year. Had to get the Senior inspector to get the sticker. In those days a was a full @$$hol!. I never had a problem after a 67 vette went through behind me one day and the guy who owned it was a state MVState inspector. The vette had side pipes. I still have the jeep, may put it back on the road at the end of the year if gas is $4.00 pre gallon. At lease the cobra handles better than the jeep, braking goes to the jeep along with 2 wheel driving. CJ's are not stable trucks at any speed. I could jump 2 lanes everytime I was passed by a tractor trailer and never move the wheel. Rick L.

[Michael C Henry]

Do you really expect to pass emissions test? In this state my car has to go through emissions testing every other year untill the car is over twenty-five years old.. I have it tested, it fails, I then have to have it repaired at a liesenced repairer. He needs to do something to improve the emissions. I'm obligated to spend up to $150 to get closer to a passing level. Anything that I spend before failing the test the first time or not through the liescenced emissions repairer doesn't go toward my waiver. I go back to the State testing station, The replica usually fails but it's better than when originally tested. I then take in the paperwork from both tests and the repairer into the office at the State emissions testing station and I leave with a waiver that I take to the DMV to get new tabs. This summer is the last time I have to go through testing with the replica.

[Ronbo]

Amazingly in a rare occurance of rational thought the legaslature here determined that emissions testing had no effect on air quality and got rid of it.

The rules here were about the same as Mike described. You could fail, do $250 worth of repairs and as long as there was some improvement, get a waiver. The next year do the same thing.

So you'd fail, makeup a fake receipt for repairs, put in some high test and fuel anti-freeze, re-test and get your waiver. Rinse and repeat.