1981 corvette carb adjustments 4 bblr feadback q-jet need idle adjust proceedure

not important, what's important is that they are absolutely clean, including the four brass high speed jets located in the bottom center portion of the carburetor.

That model engine's carburetors has fixed jets, BUT if the slow speed jets are adjustable, earlier model carburetors have been installed. If so...................

The four adjustable needle valves control the flow of fuel in relation to the set air flow, adjusted as follows (if needed).

(Dual Carb V/4 With 4 (2 each carb) Slow Speed Adjustable N/Valves)
(J. Reeves)

The adjustment procedure of the carburetor slow speed needle valves follows. NOTE... if the needle valves turn too freely, replace the nylon bearing retainer (the nylon item at the front of the carb that the needle valve goes through first) with the newer type RED retainer #315232. If your engine has that weird linkage that connects all four of those needle valves, the newer RED retainers will enable you to discard that linkage. The RED retainers make it impossible for the needle valves to vibrate out of adjustment.

(Carburetor Adjustment - 2 Slow Speed Adjustable Needle Valves, each carburetor)

Initial setting is: All (4) Slow speed valves = seat gently, then open 1-1/2 turns.

Facing the carburetors, start with the top left needle valve, then the top right valve, then the bottom let valve, then the bottom right valve. It may be necessary to redo these steps to get the adjustments ideally set

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Do not attempt to gradually adjust all four of the valves at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

You need to have the choke adjusted so it runs on a fast idle so the engine can warm up or you may need the carb to be rebuild and adjusted properly.

you may have a vacuam hose off somewhere, else adjust the throttle plate stop on the carb where the linkage comes to rest

The jets are inside the carb & there is no adjustment

You referring to adjusting the one or two idle screws
that are visible, most likely on the front of the carb in the
base plate

You can use a vacuum gauge or a tach along with it
to get the highest vacuum reading & rpm if you use a
tach also.

You do that at an idle with the vacuum gauge teed in
to a vacuum source

Then just turn the screw in about a quarter turn from the
highest reading

Have to reset the idle screw & recheck your timing
without vacuum advance hooked up.

If you can find any specs, you can use them
They most likely will use rpm as the setting point

This is not an idle adjustment. This is a vacuum leak. Check all hoses and the intake manifold gaskets.

You would get the correct carburetor instead for electronic computurized controlled carbs will not work on a 1981 Corvette

That engine runs at low speed, starts and idles on the center carb only. first make sure the carbs are synchronized so the front and rear ones are fully closed at idle, then adjust idle speed and mixture on the center carb. Sweet ride by the way, if you get tired of working on it and want to get rid of it I will take it. LOL

Most likely you have a Holley carb. You may have a 460 engine. If you have the carb with a big vacuum pot in front of the carb, then you have a RPM governor. The RPM governor will work against the 4 barrel.

The main mixture for the idle jets can be adjusted like any old style carb. You may have plastic caps over the idle screws but take them off. Then use a vacuum gauge on any intake fitting and proceed to read the vacuum level as you turn the mixture screws. You want the mixture to reach a maximum RPM, then evenly turn the screw in until the RPM drops slighty and then balance for smoothest idle.

After this step adjust curb idle and see if this helps when the 4 barrel kicks in. Holley has different springs for the vacuum actuated secondaries and they are color coded. If the carb is original it should be right, but if the carb is of unknown origin you can check the proper vacuum spring, main jet, power valve and so on in a good Holley book. The mechanical secondaries are also listed with clearances to hand adjust.

By adjusting the mixture screws you have set the engine to idle just below peak vacuum pressure. This means you should have more vacuum to work the secondaries.

could be picking up rust in fuel tank and blocking pick up, when it stops rust drops of pick up.

1982 ?? their wouldnt be any adjustment as they are fixed jet carbs ,you could try fitting new jets but whats causing them to eat away in the first place i dont know unless its the fuel additive that you have to add to the unleaded fuel