1987 threequrter ton chevy 350 moter with quadura jet carb running rich an smokeing

A 350 ci is a v8, 5.7L. What's with the 3.8L? The picture is for 350 ci--5.7L. Hope it helps?

Have you checked the computer for trouble codes yet ?

check for leak at base of carby. It sounds like the idle mixture is leaning out. check for corrosion at gaskets or loose carby body

Check all fuel lines for leaks, make sure it doesn't have bad gas in it. Listen for fuel pump when key is turned on. Change fuel filter. See if that's helps.

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I am not sure what type of Carb you have but I will assume it is a Holley ( Most Popular ) The accelerator pump arm on the carb probably needs to be adjusted.It is adjuster by bendinding the end of the arm. Also the accerlerator portion of the carb could be a bad one.The other possibility is the metering jets are too small to feed your demands of your engine on hard aceleration.Or your air/fuel mixture is incorrectly adjusted and it is runnig to lean or to rich.

thats a HUGE engine and will **** a ton of gas!!! but if ts using more than normal,along with theblack smoke,tells me you have some valves with alot of carbon buid up on them.you can spend 100s removing the heads and sericing the engine....but i would warm up the engine...have a friend give it some gas to keep the RPMs up while you SLOWELY pour a ite stream of water into th carb. it will spit and sputter while you do this,dont be scared...tats normal,then have your friend rev the engine while you do a bit more. while you do this,you will see a ton of black smoke out the exhaust. what your doing is heating up the valves,and when water hits thm, it busts that build up off,and it burns giving you some black smoke. continue to do this till the smoke changes color,and then you will have fixed it. its a trick i used years ago...and never failed!!!

clogged air filter or faulty plugs or incorrect gap on plugs

It does sound like a fuel problem, try running some jet cleaner through as you may have clogged jets. Sometimes, removal of air filter and placing the palm of your hand over the top of the carb's butterfly valve, will clear blocked jets when engine cranked over a couple of turns.
Also check the float valve is letting fuel in, could be stuck.
I hope this helps.

I've got a 91 Twin Turboed 355 that had same problem. I had my mechanic rejet the carb. It was running way too rich. That fixed that up in a jiff. Other than that, I'd recommend a full tune up. Maybe not FULL but new plugs, distributor, rotor, and def an o2 sensor.

BLACK SMOKE INDICATES RUNNING RICH.