Here is a guide to tune six packs. It's not everything but gets you close enough.
Quality cap rotor, wires and plugs that are not too hot or cold in heat range.
Distributor vacuum port on carb disconnected and plugged
Make sure that your ignition advance curve is such that you can run at 15 - 18 deg advance at idle. This is important.
Car in neutral-auto or 4 sp, emergency brake set
A good quality vacuum gage is required, a digital tach if you have that as well.
Connect vac gauge to manifold vacuum source.
Outboards idle adj screws out 1/8 turn ccw THIS IS IMPORTANT
64 jets in ctr carb
If you have new carbs(untouched) they will have 62 jets in the center carb
Black springs in the secondaries
You must know what power valve is in the ctr carb. Typically a 6.5
The slotted screw on top of the float adjuster, is just a lock screw, you can remove it for now, the 5/8" nut is the adjuster/needle seat nut, rotating it counter clockwise will raise fuel level in the bowl, clockwise will lower it
Make small 1/2 turns & let the car run a 3 or more minutes so the fuel levels off
check the fuel in the clear site window, at the bottom on the ctr carb and up to half the window the front and rear carbs,
After you set the fuel level in all 3 carbs, reset the idle on the center carb
Floats are adjusted properly
Ctr carb bottom of the sight hole
end carbs a very slight trickle out the sight hole
Starting point for Jets. center 65, front 78, rear 80. If the weather gets cold you might want to increase that to center 66, front 80, rear 82
Check the center carb and be sure to adjust the idle screw until the throttle blades are closed and the transfer slot is exposed no larger than a square. [carb would have to be off the car to see this]
You only want about .040" of the transfer slots exposed below the throttle plates.
If the idle screw is adjusted too high, you will be into the transition circuit, exposing too much of the vertical rectangular slot. Many times the idle screw is adjusted incorrectly to compensate for other issues. This puts the carb into the transition circuit and at that point you have no mixture control on the center carb.
Start car, set idle to 1000 rpm and allow engine to reach operating temp. 195 degree thermostat required or fuel will puddle in the intake. This is a must.
If the car won’t idle: Is engine vacuum reading at least 2 hg higher than the power valve rating?
This must be correct this before proceeding If ok proceed, if not correct power valve issue and proceed. Note some engines only pull 5 hg of vacuum
Now set the initial timing to where it wants to be. Somewhere between 10-20 degrees BTDC. The engine will tell you by increasing vacuum and rpm at this point. In some applications the engine does not care, so set it to 12 degrees BTDC.
Cams with 106-degree ctrlines seem to like initial timing set at 15-22 BTDC
Cams with 108-degree ctrlines seem to like initial timing set at 12-18 BTDC
Cams with 110-112 degree ctrlines seem to like initial timing set at 8-12 BTDC
center carb idle mixture screws out ccw 1.5 turns
Re-Set the rpm for 900-See if you have "control" over the idle mixture screws on the ctr carb. Using a good vacuum gage adj mixture to highest reading of vacuum. If you do not have control over the idle mixture you have issues that need to be taken care of before proceeding. Issues such as poor intake sealing, the wrong pcv valve, a vacuum leak from the brake booster or other places, wrong pwr valve etc.
Recheck idle rpm and set to 900
Drive car. Is the car rich? Jet down 2 steps until you find the min jet size. You will know when you are lean, no power.
Most times you are over jetted.... Do not over jet!
Now reset the initial timing again. Somewhere between 10-20 degrees BTDC. The engine will tell you by increasing vacuum and rpm at this point. In some applications the engine does not care, so set it to 15 degrees BTDC.
Re-Set the rpm for 900-See if you have "control" over the idle mixture screws. Using a good vacuum gage adj mixture to highest reading of vacuum.
Recheck idle rpm and set to 900
How do you know when you are "there”?
You should be able to idle most cars down to 800-900 rpm in neutral and the response is crisp. You do not smell raw gas in the exhaust. The bottom of the intake is not soaked with fuel. The spark plugs are clean. The car starts runs and drives smoothly when cold. The car restarts immediately when hot without touching the throttle. When you whack the throttle from an idle the engine immediately returns to idle.
Note: If your initial timing exceeds 12 degrees BTDC with a MP distributor typically you need to modify the advance curve so the total timing is not more than 34 degrees BTDC.
