Hi all,Im new to the forums and would like to say hi before asking questions.

Well here is the problem.I bought a all stock 1980 Z28,the car ran rough but ran,iI got it home and put new plugs/wires on it you know the whole tune up thing.It does run better but,it runs very rich(blows black smoke)and idles very high until i play with it and it comes down but not fr long.I bought a new q-jet from a buddy that was prof rebuilt and never used.I put it on the car and i have the same problem.The q-jet isnt exactly the same,the vac ports are diff and its for a 75 vette,but should work.I capped all vac ports but the one i used for the vac secondaries.With the engine running i can screw in both mixture screws all the way in with no change to how it runs.I have also changed the gasket cause i thought maybe it was sucking air.So im lost and not really sure what to do.

For the record i removed the air pump and tubes from the manifolds,but the charcoal canister is still hooked up.

 

WOW! I very shocked that i have 30 views and not one person has any ideas.

 

I just purchased an 80 Z-28 with a Q-jet it had been sitting for a couple years. It ran enough to get it on the trailer. after playing around with it i found the main throttle shaft is so worn out it must be sucking air could be your problem? The black smoke and not having any reaction w/mixture screws sound like something in the fuel metering. I rebuilt a Q-jet in vo-tech along time ago and dont remember the procedure. not sure if a vac leak would cause black smoke just poor running. sorry not much help.

 

is the choke opening? sounds like its not opening. One problem Q-Jets have is the fuel well leakes and causes a rich condtion, throtle shafts sucking air will lean it out. float level will also make it run rich.
with out seeing and hearing it its hard to say exactly whats wrong
where are you located

 

The choke is open all the way.I was messing with it lastnight,and noticed there is some fuel leaking around the rod on top of carb that goes to the accelerator pump.I guess i should give up on the q-jet and buy a holly.

 

OK,i went to jegs today and they gave me some ideas...and it sounds like firebird you was on to something,thx


1.could have a vacuum leak around the intake(i bought a vacuum guage)
2.floats are set too high.
3.come back and we will set you up with a new cam,lifters,carb and intake..for a small fee!

So ill work on this tonight and let you all know the outcome,i hope its not #3 my wife will hate that

 

That's what happens when you use a carb that has been sitting unused for any length of time. the float is stuck open. Also what CFM is it? SB chevys only need between 450 and 650 CFM depending on how it's built. I hate it when people slam the Q jet, truth is that they are just as reliable as any holley. I have owned both and I will never use another holley,between my friends and I we have owned atleast 6 or 7 holleys, they require far more maintenance than my Qjets ever needed. The Q jet on my 79 Z has been on there for 27 years never rebuilt, it's worn but it runs great and passes smog test, and I have never had to touch it. The holley on my truck would never stay in tune and did not like cold starts. It was to inconsistant for my taste. I need my truck to start when I need it, I don't have time to play with fuel mix and idle just so I can work. Since I put the new Qjet on I have had zero issues with reliability. So don't be too quick to judge the venerable Qjet.

 

I have heard that the Q-jet can be very fuel efficient and also deliver the power when u want it. I am going to leave the one on my 80 z, either have it redone or replaced. With gas prices and wanting to drive it as much as possible I think i'll be money ahead.

 

here is the update...i had a intake leak..put in new gaskets and she runs great!!!