Question about 1981 Chevrolet Corvette

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

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The idle adjustment needs to be performed warm but the mixture screws at or near the base have springs on then they need turned in all the way and backed out 2 turns then when the vehicle is warm the idle screw is near the linkage also with a spring on it if you have a tach in the car it should its a corvette lol turn the screw in or out until the car idles around 750 to 850 rpm it idles up automatically when cold if your choke is set properlythis should get you where you need to be you may need to adjust mixture screws a little the only proper way to do this is with a vacuum box but you will be in the ballpark anyway with the method i gave you

Posted on May 06, 2010

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How do you adjust idle speed 1991 johnson 100 hp


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.

Jun 28, 2017 | Cars & Trucks

1 Answer

I've a 1981 Vette that idles very rough with a cold engine start.


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.

Jan 31, 2014 | 1981 Chevrolet Corvette

2 Answers

What do I do if My 1981 corvette idles at high rpm (1500) and will not back off.


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

Apr 18, 2013 | 1981 Chevrolet Corvette

1 Answer

I need to know how to adjust the carb jets to the right setting on my 1984 ford f150 straight 6 1 barrel carb


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


Sep 14, 2011 | Ford F-150 Cars & Trucks

1 Answer

F150 79 351m carb needs adjustment, engine idles rought but runs smooth after take off


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

Jul 02, 2011 | 1981 Ford F 150

1 Answer

Looking for info on how to adjust the fuel mixture and Idle on a 1969 Corvette 427 400 HP Tri-power 3x2 carburetor.


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

Feb 22, 2010 | 1965 Chevrolet Corvette

2 Answers

I need to adjust a carberater and get the 4 barrel to start working


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.

Feb 16, 2010 | 1983 Ford F 350

1 Answer

I have an 1982 f 250 4.9 and go through carburaters a lot. New ones last may be a year then start burnning way to much gas. The carb has an idle adjustment and a curb idle adjustment no air gas mixture...


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

Jul 12, 2009 | 1982 Ford F 250

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