Quadrajet issues

[Cyanide93]

My carb had developed a bad leak out of the accelerator pump, I cleaned and rebuilt the whole thing, threw in new plugs and a coil and it fired right up. It seems to run strong but smokes like a son of a gun, it's always had blue smoke but now is a mixture of black. I've tried adjusting the idle mixture screws with no change. I bottomed both sides out which should of killed the motor? Which it didnt. Any pointers for tuning this thing?

[Coley]

First, you need to set your timing before you adjust the carb.
Make sure you have a nice amount of advance and Geezer can always give you more info on this.
This ensures that your idle is up near where it needs to be.
Then you have to dial down the (fast) idle on your truck to 600-ish rpm. Only then will those mixture screws come into effect, because they are over ridden if you have the fast idle set too high.
So timing first....get some nice 'driveable' advance on it.
After that, make sure your choke is working on the money and with the engine well warmed up, your choke plate is full/vertical and open.
Let's start with this...and maybe some of the other guys can weigh in as well.

All good
Coley

[Cyanide93]

I set the base timing about 10-12. I did notice the choke plates were not wide open at idle. I did set the idle a little high to see if the mixture screws would have any effect, which it didnt. The timing seems alright as it will brakestand with not much hesitation.

[geezer#99]

Nothing wrong with your timing or your choke. You're flooding!
Something stuck in the needle/seat, float too high or float sunk.
Fix the flooding problem first.

[Cyanide93]

I didn't adjust the float when rebuilding, was at about 1/4" from top. I did have a problem with the secondary metering rods, they seemed bent and wouldn't seat well, I had to slightly bend them out to get them to seat. They moved freely after that. Wouldn't flooding cause hesitation? It seems to run good just smokes

[B. W.]

Originally Posted by geezer#99

Nothing wrong with your timing or your choke. You're flooding!
Something stuck in the needle/seat, float too high or float sunk.
Fix the flooding problem first.

X2 Black smoke = too much fuel

[Cyanide93]

How do I know if something is wrong with the needle and seat? I replaced both with the rebuild kit

[HO455]

I would bet that one or all of your well plugs is leaking. Higher mileage Quadrajets are notorious for this issue. All the hot and cold cycles cause the factory plugs to loosen up and leak. Google it up and you find lots of info on the problem but not a lot of long term solutions.
If you let it idle for several minutes or so does it start to load up and stumble? That is a pretty good sign that you have a leak. If it is loading up look down the primary's at the venturies to see if any fuel is dripping from them while the engine is idling. At idle you shouldn't see any flow. Then open the throttle and check again for fuel dripping with it running you should see fuel atomizing but not dripping. If you are unable to see any drips it likely you have a leaking plug. Here is a pretty good info video if your interested.

How to fix a Quadrajet that floods or runs rich p…: http://youtu.be/3_Ljs7COiuE

[geezer#99]

When you rebuilt it did you install the needle clip on the float correctly? If not the needle will not sit in the seat right and cause flooding.
There's something in here about that.
http://www.crankshaftcoalition.com/w...4MV_carburetor
SEcondary rods don't effect your flooding problem.

[Cyanide93]

Are the plugs the press fit lead ones? Those had epoxy over them, someone at one time had been in it. Yes if I let it idle a while it starts to load up and stutter. The needle is just hanging on the edge of the float not clipped. I will have to crawl over it and check the venturi while its running tomorrow.

[HO455]

Yes, the well plugs are "lead ones". Unfortunately epoxy breaks down with exposure to gasoline so you may have one leaking. You can pull the carb, remove the base plate and set the center section up on some stands, then fill the float bowl and let it sit. You should be able see which plug(s) are leaking, or hit the epoxy with some compressed air and see if any of the epoxy lifts. Here are some links on this problem.

http://www.stevesnovasite.com/forums...ge=1&_k=cwjynz

http://www.hotrod.com/articles/hppp-...et-carburetor/

[Cyanide93]

So I climbed up top while it was running, the passenger venturi had fuel leaking the driver side didnt. I lowered the idle speed and it stopped leaking. The mixture screws still have no effect. Is the lead plugs my next step?

[HO455]

Try lowering your idle speed some more. You may have to adjust your timing so it will stay running. The primary flapper may yet be too high and the idle circuit is not working. There is a mechanical range the flapper must be in for the idle circuit to work. See small image. The small circle is the idle fuel port. If the flapper is open too much there will not be enough vacuum under the flapper to pull the idle mixture through that hole. Thus the idle screws (which are directly behind the hole) will not be responsive. See large image. So try to get the flapper into the correct position. You may have to pull the carb to visually check the position if you can't get the screws to start working. Lots of times there is more than one problem so one has to reset the base line and work from there. Good luck.

[Cyanide93]

I'll have to tinker some more towards the end of the week as I start shift tomorrow. But that's an excellent diagram to show me how it works. Thanks. My timing also shows about 16-18 degrees at idle, it's never ran good at anything lower since I've had the truck which makes me think maybe the timing tab is off center. I don't have one of those fancy digital timing guns to tell me.

[HO455]

You will have to check the tab by mechanically finding TopDeadCenter of number one cylinder. Then move the tab to correct any errors. Or remark the balancer. Also I believe that there is more than one size balancer for SBC's so you could have the wrong tab and it would give you erroneous timing marks. I think small tab with a big balancer reads high.

[Mike_The_Grad]

If you have a mity vac or some other means of pulling a vacuum on a tube(I would say lung power but fuel ain't good for you.) Connect it to the fuel inlet at the carb and see if it will hold a vacuum. If it doesn't, you got debris or a bad seal in the needle and seat. Don't need a ton of vacuum either, you don't want to distort the needles seal.