I would like to tune the carburator to ensure best fuel economy

Press primer until fuel fills bulb and flows out carburetor. If no fuel in primer bulb then check connections.

Check fuel line connections by disconnecting retun line to tank (without filter) and pressing primer bulb. Fuel should draw from tank (filter), into bulb, out bulb to carb and expel out carburetor. If not the bad lines, filter, or lines not connected correctly.

With fuel primed, turn both high and low speed needles in (CW) until seated, do not tighten. Then turn needles out 1 1/2 turns for initial settings. These settings are only to get unit running. Increase idle speed setting if engine stalls. Adjust low speed, then high speed and lower idle speed back to normal.

Edelbrock cars are square bore and Quadrajets are spreadbore make sure you have either an adaptor plate if running stock manifold or you'll have vacuum leaks, as far as tuning Edelbrocks are EZ. 2 air/fuels screws that only effect idle, turn in till runs rough then back out 1/4 to 1/2 turn on both, that will set it for economy, for performance engines, turn out or counter clockwise till runs rough then turn back in clockwise 1/2 to full turn, set idle ***** and your good to go, the two vacuum ports in front are distributor advance, the right side closest to manifold is full time vacuum hook there for performance or left side for economy.. if you buy a new edelbrock carb it will run great right out of the box, also has a set/up DVD, for novice Mechanics, ez to change metering rods too, hope this helps, and in my opinion Quadrapuke carbs are junk.

You need to hone the accelerator pump well and adjust the throw of the pump rod as much as possible to get more fuel. Of course that is just a guess based on 100's of rebuilds i have done over the years. I have also found that Japanese carbs seldom turn out when rebuilt.

Ensure you have the ignition timing set correctly for the engine you now have. Ensure you have no vacuum leaks, unplugged lines at the manifold or carb.
I would discourage trying DIY on gas as its very dangerous. professional fitted use brass spanners and tools to avoid sparks igniting the gas. i would suggest you bring it to a specialist.

PROMLEM MAY BE BECAUSE LOW IDLE SPEED ADJUSTMENT. INCREASE THE LOW SPEED/ IDLE SPEED BY INCREASING THE FUEL INTAKE . IN CARBURATOR VEH. ADJUST THE IDLE SCREW CLOCKWISE. IF IT IS FUEL INJECTOR INCREASE THE FUEL AT PUMP ITSELF.

the air fuel adjustment has little to do with what u have going on, but here is what u do, make sure the engine is at normal operating temp temperature (at least 185F) then verify idle speed is set to spec +or- 50 RPM, then turn the carb mixture adjusment screw in until the idle speed starts to drop off, then turn it back out until the idle speed increases to its highest point (u will need a hand held tachometer), when u have reached the highest idle turn the idle screw back in 1/4 trun, that is lean best idle.

Hello:;
This sounds like a fuel problem at the carb. What it's doing is termened hunting a nd can generally be corrected by a simple adjustment of the carb. Engine at idle and neutral set rpms at lowest idle , around 640 rpms. then adjust the a/f ratio screws to balance carb. Screw both screws all the way in, do not force ,or needle and sear damage will occir. Now back each out to 1.5 turns That is your start point Adjust one screw in and out slowly until you you feel its best effact on ide whicjh should slightly increase. repeat with other screw, in and out slowly . listening to the engine idle. if idle has increase due to your adjustmebt, repwat process after lowering the idle speed again with the idle screw. When you get to the point the screws no longer affect the idle the engine show sound and run smoothly at idle, make sure you resert the idle to 650rpms for an automatic trans and 650-750 for manual trans. I hoped this helped- good luck.. If it still does it, the carb may nrrd the float checked and st.

Before you start check the status of your choke. One that is stuck on will cause a high idle. If the choke checks out, proceed to the following:


You should have what's called a 2 needle carburetor. A larger screw adjustment for idle, and a smaller for high speed.

Start by adjusting your low speed (idle) needle until you reach the desired idle. I prefer about 850rpms. Do this with the engine running and adequately warmed so that your adjustments are not thrown off by the automatic choke.

Next slowly open up the high speed needle. As you open it your idle speed will gradually increase. Adust it in 1/8 turn increments, pausing after each adjustment to allow the changes to take affect. Keep opening it until you stop increasing your rpms, then take it back 1/8 of a turn.

Next readjust your idle mixture screw so that your idle is back down to 850rpms.

U are not describing a carb adjustment issue but a carb dirt issue or an intake manifold leak or the base of the carb is loose (very,very common), twist the carb body if it moves the base of carb has come loose, but back to the adjustments, set the rough idle speed to spec, then turn the mixture screw out about 3 1/2 turns, then turn slowly in while you watch a hand held tach, when the eng reaches its maxium idle speed the mixture is correct, then turn it in 1/3 more to pass smog and maximize fuel economy, then set the final idle with the idle speed screw, also verify the dash pot works so the throttle closes slowly when you raise rpm, if the little decel dashpot is no good replace it.

You will need a vacuum and Tach meter guage, when the highest vaccum/RPM reading is reached the air fuel is near perfect, make sure you start lean and slowly turn the mixture screws out ( or in depending on carb type) evenly, reset idle speed if ness, as it can increase allot. In order to meet emission tests and get better fuel economy I would lean each screw 1/4 turn from best vaccum/RPM setting. Also verify the ignition timing is correct before any adjustment is made and engine is at operating temp.