You need 6 good cylinders! Do a Compression Check!
You need the TIMING / point gap-dwell SET correctly BEFORE attempting
note: timing must be set BELOW 800 rpm! with Vacumn Advance hose plugged!
You need to DISCONNECT the driver's side linkage!!!
You need 2 GOOD CARBS! [ test by opening just ONE carb at a time to see if engine runs the same for both!].
You need TIGHT linkage..do what is necessary to stop side movement in the crossshaft and slop in any of the holes…BUT make sure linkage is not binding!
You need the engine fully warmed up AND make sure the CHOKES are fully opened!
If using a UniSyn, or other device ON TOP of the carbs....make sure the Choke plate is not hitting the device!
You need 2 good carb bodies! If the Choke shaft hole[s] are worn...AIR LEAK! [ apply thick grease to plug temporarily!]
If using a "U-Tube" / Magnahelic GAUGE...make sure you are connected to the HORIZONTAL ports! [choke pulloffs!].
If you are using the carbs for the 1st time / engine startup, etc., hold the choke open, back out idle SPEED screw until throttle is totally closed......slowly screw in until you feel / see the throttle just start to move..than 4 turns more! Idle MIXTURE screws should be 2 turns out from seated [ closed fully ].
NOTE: TO BALANCE THE CARBS…..YOU ARE ADJUSTING AIRFLOW ONLY/ IDLE SPEED SCREWS!!! NOT THE IDLE MIXTURE SCREWS.
ONLY AFTER GETTING THE AIRFLOW BALANCED, AND IDLE SPEED DOWN LOW [ 500-700 RPMS] DO YOU THEN ADJUST IDLE MIXTURE SCREWS TO MAKE THE IDLE SMOOTHER!!!!
With UniSyn Balancer
With engine running on it’s own….steady RPM…..
Set UniSyn on top of the LEFT carb. Adjust the thumbscrew wheel [in center] to get the Ball at one of the LINES! Any line! Preferably in the middle!
1 Without touching anything…..set on RIGHT carb…..look at / for ball
If the Ball is seen BELOW the LINE that the LEFT carb was at, or doesn’t rise at all……
Turn the RIGHT carb’s IDLE SPEED SCREW IN!! Do this until the ball is at the same line as the LEFT carb WAS. DO NOT worry about ENGINE SPEED now!
If RIGHT carbs’ ball is ABOVE the line the LEFT carb was at……BACK OUT RIGHT carb’s IDLE SPEED SCREW until it’s at the same line as the LEFT carb. DO NOT worry about ENGINE SPEED now, unless engine died. If it died, then TURN IN the LEFT carb’s IDLE SPEED SCREW 2 turns….and start over [ go to “1”].
WHEN UniSyn shows EQUAL BALL position….determine if idle speed is where you want it. DO NOT worry about rough idle NOW…..as long as it continues to run.
2 If IDLE SPEED is too FAST…….BACK OUT BOTH carbs IDLE SPEED SCREWS EQUALLY to get the speed you want.
RECHECK AIRFLOW [balance] Go to “1”.
If IDLE SPEED is too SLOW…….TURN IN BOTH carbs IDLE SPEED SCREWS EQUALLY to get the speed you want.
RECHECK AIRFLOW [balance] Go to “1”.
3 When you are satisfied you may now adjust the idle MIXTURE screws to get the smoothest idle possible!
4 When you are satisfied with idle OPEN ONE carb at a time to see that the engine runs the same on both sides, AND that the engine returns to the same idle speed. If not..find and fix the binding / cause.
4 When EVERYTHING is fine…SHUT OFF ENGINE…...WITHOUT MOVING EITHER CARB or CROSSHAFT, carefully adjust swivel on drivers side to just slip in the hole…..attach with clip.
5 Start engine, and RECHECK AIRFLOW / BALANCE [ go to “1”].
Using a “U-tube / Water manometer”, or other GAUGE with 2 ports / “0” Center [ Magnahelic, etc.]
Look at the NEEDLE [gauge] or the Water Levels [ U-tube].
If the needle is to the LEFT , Water level is HIGHER on the left, BACK out IDLE SPEED SCREW on LEFT carb.
If the needle is to the RIGHT , Water level is HIGHER on the right, BACK out IDLE SPEED SCREW on RIGHT carb.
When BALANCE / AIRFLOW is satisfactory
GO TO “2” and proceed thru “5”
NOTE: depending on your air filter[s]
YOU MAY NEED TO RE-ADJUST the IDLE MIXTURES to obtain a smooth idle, etc!
DO NOT adjust IDLE SPEED SCREWS!!!