Hello everyone I have some trouble with my carburetor. I just bought the car and I'm trying to smog it . I went to smog it and the technician told me the car failed only because it is running rich. My question is... Is it possible to adjust the flow, how hard is it to do? The carb and engine are original.....

 

Not really possible to "adjust the flow".

Most likely cause of running rich in a smog-test situation, is the plugs on the bottom leaking.

If you take off the carb (use a 5/8" flare-nut wrench on the fuel line nut and a 1" open-end on the big inlet nut!!!!), remove the 2 rearmost air horn screws, flip it upside down, and remove the throttle plate, you will see 2 large plugs about the size of a dime near the center of the carb, and several sort of "tower" looking casting features at the front. The dime-sized plugs aren't the problem so ignore anybody that tells you to mess with them. The "tower" things though, each have a couple of much smaller plugs, maybe 3/16" dia, spun into them. THOSE are not the same kind of metal as the carb body, and cause the dissimilar-metal corrosion problem, which erodes the chinesium that the carb is cast from. There is vacuum (SUCTION) on the outside of the plugs, and the bottom of the fuel bowl (LIQUID GASOLINE) on the inside. Eventually the carb body gets so far corroded that fuel is sucked around the plugs like a wet/dry vacuum cleaner, DIRECTLY INTO the intake, thereby COMPLETELY BYPASSING the entire fuel metering apparatus of the carb. Therefore NO AMOUNT OF ADJUSTING will EVER cure this problem, it MUST BE fixed at the source. The effect is most severe at idle and cruise, when vacuum is high; this has almost no effect at all on full-power operation because then vacuum is at its lowest.

Solution is, take a wire brush to them, and clean them all down to bare pristine metal (at which point you might even be able to see the white powder corrosion where the 2 different metals touch); sterilize them with some sort of NON-RESIDUE cleaner such as lacquer thinner, acetone, MEK, or denatured alcohol BUT NOT brake parts cleaner or engine degreaser; and epoxy over them liberally with JB Weld or similar epoxy w steel filler. After getting every possible trace of gasoline out of the carb body, put the fuel bowl in the oven at the lowest possible setting for a couple of hours to completely harden the epoxy.

While you're at it, the fuel filter is behind that 1" nut. Pop that off and replace it. BE SUPER CAREFUL not to cross-thread the nut putting it back together. Same for the fuel line nut; thread it all the way up by hand BEFORE TOUCHING IT with a tool. Use no sealer on anything, only a little silicone dielectric grease on the threads of the fuel line nut.

 

i had the same issue with mine years ago when I ran my 305 in it. In addition to what Sofa suggests...how old is your cat convertor? I had my original monolithic cat on mine...

Even after I went through everything to ensure it was up to spec, it still failed. I put in a new aftermarket cat, had to have the 4 bolt flange welded on each end...and it passed with less than half the emissions!! All that being said, if you have a carb issue, get that straightened out first and see if it'll pass. If it's ran a long time running rich though, your cat is probably toast. Just a thought.

 

Just an FYI: Catco makes the correct after market (Vin G) cat. IIRC, from Summit, the number is CAT-4116.

JamesC

 

That's good info! They didn't carry it 6 or so years ago when I replaced mine....or no one knew about it...and you don't want to know how much a stock replacement was...

 

Thanks guys I appreciate your time and knowledge .... Well so far I have jbweld the plugs on the bottom of the carb, I went and installed a new cat, and I timed the car at 6 degrees without vacuum advance, but now I'm trying to adjust the mixture screws and I don't know what the intake manifold vacuum should read at.... The car idles around 800 rpms and the vacuum reads at 18 in Hg..

 

With a factory cam...the intake should read about 22" of vacuum or there about. Don't touch the mixture screws...those should never change. HOWEVER, if you already have, and I'm talking the big ones on the front of the carb, turn them all the way in until seated, then back them out 3.5-4 turns. Turn them both out the same amount. Unless you have a wide-band 02 sensor to tune the exhaust, you don't want to touch them. All things considered, if it's still failing after plugging those holes up, I'd suggest a full rebuild of the carb...which suprisingly, doesn't really deal with the mixture screws unless you want to (my rebuild didn't require it but I also decided to send mine off to have it professionally rebuilt).