[al lkosmal]

We will need to know a bit more regarding how you proceeded with the initial set up. The out of the box set up should have been a decent starting point, but did you follow the initial start up adjustments, then adjust vacuum, side to side balance, mixture and idle? Is it possible that you just have your mixture adjustment set too rich?

(from an earlier Pelican post)

Weber Set-up
Part I

STEP 1- Accelerator Pump Volume
Measure the accelerator pump volume at each of the 6 nozzles. Before starting the car, turn the key “on” and energize the fuel pump. Let the pump run a minute or so to fill up the float bowls. The air cleaners are off. Now, lower the vial down the throat of barrel No. 1 and park it directly under the nozzle. Have the assistant in the car depress the gas pedal all the way, nice and easy. Withdraw the vial, record the results on a piece of paper, and dump the contents of the vial. Repeat at each nozzle. (You may have to remove the velocity stacks for cylinders 2, 3 and 6 to gain proper access to the nozzles for those barrels.) Adjust the nut on the accelerator pump rod as necessary. Turning the adjuster nut out will increase the amount injected, and vica versa. You want .6 to .8cc (ml) (.75cc works great). Get them all even.

This procedure can also be done on the bench. Just fill the float bowl that has the brass valve in the bottom that feeds fuel to the accelerator pump. Then activate the pump and measure. The advantage of measuring at this stage, as opposed to when the carburetors are attached to the intake manifolds, is that if there is a blockage, it is easy to get at the check valves, nozzles, pumps, and float bowl valves and clean them out.

This procedure also provides a good opportunity to check that the throttle plates are opening all the way (vertical) with the gas pedal floored. If they are not, turn the plastic adjuster under the gas pedal in to give more travel, or out (less travel) if the throttle plates rotate beyond the vertical position.

STEP 2- Float Level Adjustment
Remove one of the two float bowl plugs on one of the carbs. There are two plugs per carb since there are two float bowls and two floats per carb. Careful- all the fuel in the float bowl will dump out so catch it with a little jar. Now insert the tool and tighten it to prevent leaking, since any leaking at the washer will give false readings. You need to focus on the upper two lines scribed on the vial portion of the tool. The lower two lines are for the Zenith carbs that some 911T's used (70-71). Have the assistant turn on the key to energize the pump but don't try to start the car. Now the float bowl will fill and you'll see gas fill the vial. After the vial is through filling, carefully examine where the meniscus is. You want it right between the top two lines. Turn off the key. Remove the needle valve plug, back out the needle valve and seat and add or subtract washers as necessary to raise or lower the fuel level, respectively. (ADD SHIMS= INCREASE FUEL LEVEL; REMOVE SHIMS= DECREASE FUEL LEVEL). Replace the needle valve and seat and the plug and have the assistant turn on the key. Note the fuel level. Continue to adjust until the meniscus is spot-on. The washers that come with the tool differ in thickness. After you do one, you will develop a sense for how many washers you need to raise/lower the fuel level. Then remove the other float bowl plug on the same carb and repeat the process. Keep at it until you've got them all perfect.

A couple of things- some books say to measure the fuel level with the car running. I've tried it that way and believe me, it's pretty hard to do since the engine is vibrating when it’s running. This vibration makes the fuel is slosh around in the vial and thus it becomes difficult to determine if the level is correct. This is exacerbated by the fact that the two lines scribed on the vial are near the very top of the vial. Second point-- the washers under the float bowl plugs are crush washers that are good for one shot. After you replace the plugs, if you re-use the washers, they are likely to leak. If you have some extra ones, use them. If you don't, don't overtighten the little bastards. Just snug them and move on. You can always order more from PMO and then go back and replace them at your convenience.

STEP 3- Initial Start-up Adjustments
Make the initial adjustments to the screws as per PMO and fire it up.

Initial adjustments (PMO) are as follows:
Idle air correction: 1/8 turn out*
idle screws: ½ turn in after touching throttle arm on each carb
idle mixture screws: 2 turns out

(*I suggest turning all the idle air correction screws in (gently!) until they hit their seats, and lock them down for the initial start up. You want a nice rich mixture for starters to avoid excessive popping which is really distracting, and then work from there.)

Here is where it gets tricky- while your assistant in the car keeps the motor running by judicious applications of throttle so that the engine warms, you have to diagnose in a grossly rough way, what is going on and what you need to do to smooth out the idle so that you can get the car running tolerably well enough to begin the real work of balance, synchronization, mixture adjustment and idle speed adjustment.

If the engine idles (regardless of speed) with the initial settings, do the following: if any barrel is spitting, slowly open the mixture screw- like 1/8 of a turn at a time. This should reduce the incidence of popping/spitting. Once the popping is reduced, quickly measure vacuum on each barrel with your STE. Are the barrels of each carb pulling roughly the same vacuum? If not, and vacuum is all over the place, determine which carb is pulling, on average, more vacuum than the other. Then open up the idle stop screw on the carb that pulls less vacuum, or turn in the idle stop screw on the carb that pulls more vacuum, or both, so as to get both sides roughly equal. Keep engine speed close to idle speed (900 rpm).

If the engine won’t idle, have the assistant hold it at a faster speed and adjust the mixture screws to avoid excessive popping. Once the engine runs smoothly, release the gas pedal and see if it idles. Check vacuum and make any adjustments to the idle stop screws that are necessary to get the car to run at idle. Once the car is warm (140 degrees or better) and holding an idle, it is ready for accurately setting balance, sync, mix and idle speed.

END PART I