[T Bird]

Cerbin
Part II below.
John

Weber Set-up
Part II

STEP 4- Vacuum Adjustment- (balance)
Disconnect the right and left carbs from the crossbar by undoing the short press rods on each carb. Use an 8-mm wrench to pop the ball cups free of the throttle arms. You don't want the linkage affecting this adjustment. Pick a carb. At 900 rpm, measure vacuum at each barrel and record results. Determine which barrel pulls the most vacuum (“reference barrel”). Lock down the jam nut on that barrel’s idle air correction screw. Now, carefully and slowly turn out the idle air correction screw on one of the two barrels that doesn't pull as much vacuum as the reference barrel. Get the vacuum exactly equal to the reference barrel. As you open the idle air screw to equalize vacuum, you are going to experience popping, since you are leaning out the mixture by introducing more air into that barrel's idle mixture. DON"T PANIC! Just open the mixture screw up a hair to compensate so that the popping doesn't distract you, or if it's just occasional popping, you can leave it alone for the moment. When vacuum is equal to the reference barrel, lock down the jam nut. Equalize vacuum in the remaining barrel the same way.

Now, you have all three barrels on the one carb pulling equal vacuum. Repeat the process for the other carb.

Step 5- Side-to-Side Balance @ Idle (synchronization)
Using the STE synchrometer, determine which side is pulling more vacuum. Turn the idle stop screws out or in a hair until both sides are pulling equal vacuum and you have 900 rpm idle. Turn the idle stop screws in to speed or out to slow, keeping each side balanced with the other. Now, the engine should be running at 900 rpm with each barrel pulling exactly equal vacuum. You are probably getting an occasional pop since your mixtures are all off.

Step 6- Side-to-Side Balance @ 3000 RPM (synchronization)
Reattach the press rods. Check the side-to-side balance at idle to make sure that the linkage isn't off at idle. If the press rods disturb the idle balance, adjust them so that they exert no preload on the carb throttles. Now you are ready for balance at 3000 rpm. Have the assistant hold the engine at 3000 rpm. Quickly run the STE over each barrel and record the results. Each barrel of each carb will match. But, your linkage could be off, causing the right carb to be out of sync with the left—that is, one carb may be pulling more vacuum than the other at 3000 rpm. If one carb is pulling more vacuum than the other @ 3000 rpm, lengthen or shorten the right/left press rods to compensate. When you get vacuum to balance at 3000 rpm, check that the linkage adjustment hasn’t screwed up idle balance. When vacuum balances at idle and at 3000 rpm, you are synchronized and ready for the "artful" part of this process, where it helps to have the ear of a musician.

Step 7- Mixture Adjustment
Speed the car to 1200 rpm using the hand throttle in the car to hold it there. (This is the BA method- put rock on gas pedal. PMO advises to disconnect the right press rod and speed the engine with the idle stop screws. I use the BA method.) Now start with barrel 1. Slowly turn the mixture screw in until you hear slight popping in the muffler- a little more and the idle speed drops. You may get an occasional BIG POP while doing this- this is normal. As soon as the idle speed drops, slowly turn out the screw until idle speed comes back up- this should take about 1/8 of a turn. You may hear that faint popping in the muffler at this point. If you do, turn the screw out a bit more until the popping disappears and the engine runs smoothly. (NOTE: Slow turns on the screw are warranted. Reaction to changes in the screw’s position is not immediate.) Now, note the position of the screw and slowly give it 1/2 a turn more. This is the initial setting. If it continues to pop or spit up before moving on to the next barrel, turn out the mixture screw an additional 1/8 turn. All should be well with that barrel for the moment. Proceed to barrel 2- same process- then 3, 4, 5 and 6. If it took ½ plus 1/8 of a turn to get barrel 1 to behave, then turn out the mixture adjustment screws for all of the other barrels the exact same amount.

After you run through them once, you will have some doubts as to whether you got the mixture on the first few barrels equal, since as you move through this process, you will begin to develop the "ear" and the "feel." Start over with barrel 1. Make sure that each screw is turned out the same amount from that point where the idle speed returns without faint exhaust popping after it has dropped as a result of turning it in. The point here is to get them all equal. Run through them as many times as it takes to smooth out all popping and spit ups and to get satisfied that you have them all open the same.

Step 8- Idle Speed Adjustment
Release the hand throttle and let the engine return to idle speed. If idle speed is off, disconnect the right and left press rods. Adjust the idle speed to 900 rpm with the idle stop screws. Make sure that side-to-side vacuum remains equal. The engine should be running smooth- no popping and holding a nice idle. Reconnect the press rods and check balance at idle and at 3000 rpm again just to be sure!

Step 9- Test Drive
Take the car for a test ride. Is there any surging between 2000 and 3000 rpm? Is it popping on deceleration? Is it transitioning seamlessly between idle and main circuits? That is, no flat spots, right?

Return to home base. Make any final adjustments that you feel are necessary to the mixture screws. In other words, if it popped occasionally or surged, turn all mixture screws out an extra 1/8. Repeat test ride. Make any further adjustments that are necessary.

If the mixture screws are turned out more than 3 ½ turns from full in, the idle jets are too small. If the engine stumbles on acceleration or is slow to return to idle, the idle jets are too small.

End Part II