I have a 305 with a Non feed-back Q-jet and I can NOT get this thing to run right. Full throttle seems to be ok, but when you back off to a cruise, it has a misfire. I also can not get the car to idle below 20 degrees BTDC. It also ALWAYS smells very rich and the plugs look that way as well, not wet but sooty. If I try to idle it up via the idle screw any more than it is now, it dribbles from the primaries...I am at wits end and do not know what to do next. Any suggestions?

-Rob  

IT sounds like you may have a vacuum leak.I would check all the vacuum hoses for any vacuum leaks you may have.  

there's an excellent QJ site with everthing needed to tune them. search 'quadrajet tuning', hope it helps!  

there are several things.. does it have the large vacuum valve above the thermostat.. that sometimes fails and causes leaks from the vapor canister..

have you tested the egr valve????  sometimes they leak wne closed... usually do to carbon on the pintle...

and chance that someone installed teflon tape on the fuel inlet..???? teflon on inverted flair fittings is a no no...  and on the fuel filter inlet also.. the tape will get into the needle and seat and cause all kinds of havoc...

did the trapdoor (efe valve)  on the passenger side exhaust manfold stick closed or loose its vacuum source and cause the carb mounting gasket to burn up....

i have also seen the Q jet  main carb  body to base plate gasket burn out...

one last thing.. is there anything trapped in the throttle blades???   dirt ,,, sticks,,, debris.,????? that has made a bunch of cars hard to idle...

post the year if it is orignal.. az has vacuum diagrams and more info on their web site under repair info...  

Hey guys, thanks for the help so far. It has no EGR or EFE, I have checked for any and all vacuum leaks, and found none. The carb itself was obtained about 2 years ago from a reputable remanufacturer. I had installed it on a vehicle at that time, then lost interest in that vehicle. I had never put a vacuum gage on it when it was in that car. It does have a Comp Cams XE262 so the idle is a bit lumpy...The best I can get at idle was about 13.5-15" but it still seems rich. I know that these CAN be good carbs if they are "right", should I just throw in the towel and install something else?  

If you are sure its the carb. then I would install something else I recomend a holley something around 450CFM holleys are the only carbs. I use and never had any problems from them.I have had Q-jets before and always had problems out of them also did you check the fuel filter on your Q-jet.  

I did, everything looked "normal"....no debris on filter, spring was present, etc.  

Also you might want to check the oil if it smells like it has fuel in it then the carb. needs to be replaced or rebuilt.  

Here's another possibility. Check your ported vacuum switch to see if it's working properly. I've seen on the emissions loaded cars, if this valve stops working, vacuum won't be routed properly, and the motor runs like crap.

The switch is located on the intake manifold, usually around the thermostat, and works of engine temp. As the coolant heats up, the switch will divert vacuum to a different line.  

I disassembled the carb today...WOW at the sediment in the bowl! I'll test my rebuilding skills (or lack there of)tomorrow and see how that goes.  

You may want to get a new float as well they usually do not come with the kit.  

Yeah got that too, I guess if it runs worse this time, its all MY fault. I haven't done one of these in years, and that one ran long enough for me to drive the $200 '79 Camaro home...I think I have a much better understanding as to what I might actually be doing this time though. It's amazing to think back at all of the stupid things I have done when I was younger...

-Rob  

Just to let you all know, it DOESN"T run like poop no more! I rebuilt the carb and stabbed new plugs in it. It was better after the carb and the misfire disappeared completely after the new plugs. Number 6 had a really tight gap...I might have done that upon installation being that its the hardest one to get to with these FlowTech shorty headers. Anyway, thanks to all of you that replied, your input was worth a million! I'd like to wish you all a "Merry" and "Happy". Once again, THANKS!!

-Rob