Carb adjustment !?

[kasi]

Hi guy,s !
I have an Duetto Spider 1.6 from 67 with 2 double 40 DCOE 27 ! I just weld a Lambda Sonde in my exhaust system wich i connect to a small computer so that i can see my Air /Fuel mix !!
I have the car now a half year it it never drove good on low rpm and it was never idling steady !!
So today i was driving with my computer and it showed me that the car run's a way to rich on low rpm !
That means ,during acceleration i got a mix around Lambda 0.70 ! Between 3750 and 6000 rpm the car runs great and i got Lambda 0.95 !!
accelerator pump jets 35
venturis 32
main jets 115

so what am i supposed to do now ??
Thank's in advance
Kasi

[joecautela]

Kasi, Read up on the weber base adjustments, then ck the sizing of your idle jets. After that take a peek at the position of the throttle plates in relation to the progression holes (description and drwg in the weber book). Sync (balance) the carbs. Set the timing. Repeat above. It can be tedious. Ck the points for correct setting. I'm slightly out of order here. Points and base adjustments first. Set timing. and so on. You'll get the hang of it. Roughly 3/4 turns out on idle mixture screws. Listen for the "sweet spot" in the mixture adjustment. I would definately read up first on your carbs. Good luck, Joe ps. One thing. On your idle adjustment screw. Make sure you are backed out far enough to ensure the throttle plates are fully closing, letting it run strictly on the idle circuit. A few turns in and you now have entered the progressive portion of the circuit and it will do what you are describing now, Joe

[Ianc]

Here goes from a 30 year-old memory. Well, a 62 year-old memory thinking back 30 years. Loosen the connector clamp between the carbs, so each throttle is acting on its own. The manual tells you to remove the two plugs above the throttle plates and line the plates up in the holes, which works on a new engine but not on an old one. Either find a manometer and balance the carbs, or find a 30 cm long piece of 1 cm diameter tube and listen to one carb and then the other, adjusting the throttle plates until the sound is the same and the idle speed is about 900 RPM. Now see what you have on the gauge. If still NG, let us know.

[60sRacer]

Lots of the old carb cars were rich at idle speeds. Gave a bit better acceleration. Be sure to check your plugs; the original Lodge 2HL's tended to carbon up and foul at idle. The lambda is somewhat inaccurate at low speeds too.

R

[kasi]

Ok Guy's !
I opened the distributer and the inside look's brand new ! I have also an upgrade to pointless ignition ! I set the timing to the F mark (4-6 deg BTDC ) according to my book ! If i open the 4 screws, i see in each hole 3 holes, the throttle plattes covers the 1st hole complete and the 2nd to the half (in all 4 holes ) using a mirror and a flashlight !!
That means the carbs are sync/balanced ,or am i wrong ???
For the plugs i have to check ,can't remember wichone i'm using !
Tha carb setup is correct according to the weber book !!
But i'll check it out !!
Thank's a lot
Kasi

[kasi]

Ok Guy's !
I opened the distributer and the inside look's brand new ! I have also an upgrade to pointless ignition ! I set the timing to the F mark (4-6 deg BTDC ) according to my book ! If i open the 4 screws, i see in each hole 3 holes, the throttle plattes covers the 1st hole complete and the 2nd to the half (in all 4 holes ) using a mirror and a flashlight !!
That means the carbs are sync/balanced ,or am i wrong ???
For the plugs i have to check ,can't remember wichone i'm using !
Tha carb setup is correct according to the weber book !!
But i'll check it out !!
Thank's a lot
Kasi

[60sRacer]

Check the distributor advance with a timing light with the car idling. The advance weights are controlled by small springs that can age, which will also make idle eratic. Similarly, poor spark plug gaps can cause rough idle, as can fouled plugs which is very common on carb alfas with cold plugs.

Also be sure to check the valve clearances and the cam timing, and adjust the slack in the timing chain.

Another issue may be that the carb float valve seat is worn, leading to uneven fuel level in the carbs. And while your at that, any varnish or gum deposits form old fuel tends to collect in the carb bottom and can foul the jets very small orifices. It'll take a carb overhaul to really be sure the carbs are clean, but try some carb cleaner in them. [take the top cover off with the screws, drain the fuel, unscrew and remove the jets, spray some carb cleaner in the bottom especially of the jet bores, soak the jets themselves in cleaner, rinse all with alcohol, reassemble].

Be sure to replace the small paper fuel filter too. Drain the gas tank and add some good fuel.

R

[Ianc]

So much for my memory. The first thing to do is check the float levels. The level of gas in the bowls determines the level in the various circuits. If the floats are not at the same (correct) level, you'll never get the carbs right.

[kasi]

Hy Guy's !
I just studied my Weber book's and there is written that a fuel pressure higher than 3.5 psi will float the carb's !
I have an electric low pressure fuel pump and i get around 7 psi !!
Can this cause my problems ????

[kasi]

I checked also the float level using a 9 mm Drill ( same diameter as the nedle valve ) !
I put the drill between the float and the float bowl cover ( with gasket )! the tab was slighly touching the needle valve !
Is that correct ??

[Ianc]

Quote:

Originally Posted by kasi Hy Guy's ! I just studied my Weber book's and there is written that a fuel pressure higher than 3.5 psi will float the carb's ! I have an electric low pressure fuel pump and i get around 7 psi !! Can this cause my problems ????

[60sRacer]

The stock carb cars have a combination fuel filter (with replacible paper filter and glass bowl) and pressure regulator, generally set for 3 to 4 psi. Most racers put a permanent fuel pressure guage on the line. the stock item is mounted on the side rail outboard of the distributor.

R

[alfaparticle]

If you have excessive fuel pressure you will probably see a film of gasoline in the intakes of the Webers due to flooding. Fuel pressure regulators are not expensive. The Weber suppliers or race car parts people have them. I bought 2 on ebay for about $20.

There is a specification for the level of gas in the jet wells. It should be in your Weber book. It is a measurement from the top of the carb to the liquid level. Get a long nail and mark these upper and lower limits from the tip of the nail. Run the car for a minute or so then turn off the engine. Remove the circular covers from the top of the carbs. Remove one main jet stack from each carb. Shine a flashlight beam into the well so that you can see the liquid level. lower the nail into a well until it just touches the liquid surface. Check the marks that you made against the top of the carb body. Repeat on the other carb. If the levels are different, then you need to adjust one of your floats. If they are both wrong by the same amount, go back and double check your measurements.

I always follow this procedure before I start bending tabs on floats.

Ed Prytherch, Columbia SC
74 GTV
79 Spider
88 Verde

[jimr]

Quote:

Originally Posted by kasi Hy Guy's ! I just studied my Weber book's and there is written that a fuel pressure higher than 3.5 psi will float the carb's ! I have an electric low pressure fuel pump and i get around 7 psi !! Can this cause my problems ????

[joecautela]

I had one of the aftermarket rotary dial regulators and did experience flooding, even when lowering it to 1.5. I replaced it with the original fisa filter/regulator unit and problem solved. In this case once again the "Factory" knows best!