Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Needle seat question

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Bigal442:
Let's suppose that someone forgot to include that tiny needle spring clip upon a rebuild, would this matter and what would the effect be? Yes the needle clip was left off during my rebuild. Obviously when the float arm is pushing it down it won't matter but will the needle return upward properly? I can't find the clip that came with the new needle but I have an old one I could use. Not too excited about going back in but will if I need to. Comments?

429bbf:
to each his own . i throw them away on rebuild. haven't had any problem .having one in there hooked up wrong (seen this quite a few times )causes way more problems. hth

Bigal442:
Thanks for the reply. I wouldn't think the clip would be the source of my trouble but I thought I would ask. I suppose it's time to elaborate since I am getting frustrated and out of ideas.

I just rebuilt my Q-jet (17059205) with Cliff's HP kit + a few extra things like a new pull-off, main jets, DA secondary rods, etc. The carb goes on a 454 chevy 9.5 to 1, roller cam .222/.226 @ .050" 110LSA and .550" lift, headers, stock heads and intake. I followed Cliff's advise and ended up with the following:

idle tubes .039"
channel restrictors .055"
upper idle bleeds in main casting .070"
lower idle bleeds reduced to .067"
main air bleeds in horn only .087"
bypass air started at .110 but ended up at .125"
main jets .073" with 52m primary rods (original)
Orange power piston spring
Idle mixture holes drilled to .093"
Float is set around 9/32"
Secondary rods DA with "I" hanger
Carb has APT with external adjustment through the top

So what is going on? The car is running super rich!!! Plugs are now black with carbon. Makes me think I did something fundamentally wrong during the rebuild (got a question in a minute). The car will idle okay when I leave off the APT 3/8" plug (found this by accident). This is causing a vacuum leak which seems to confirm that it's running way to rich and likes the added air. If I put the APT plug back in it idles rough and is loading up. I have the metric idle mixture  screws only out about 4 or 5 turns with no nozzle drip. However the idle screws don't seem to be doing much, meaning they don't change my vacuum or rpms. From what I read 4 or 5 turns with these metric screws should not be all that rich. The car actually has decent part throttle response despite putting out some black smoke according to my father-in-law when following me. However, when I get into the secondaries it really puts out enough of black smoke to see in the rear view mirror and is "bucking" pretty hard. It seems as though it's just drinking gas.

Now for the dump question that I hope could be the source of why it is running so rich... Does the power piston (really the small rod that sticks out of the power piston that hits the APT) sit on top of the APT or does it go in below the APT? In other words, does the APT control how far the power piston goes down or how far it can come up? Not sure it's even possible to get this wrong but I am think I have something majorly wrong (vs. just some tuning) for this thing to run this rich. This is how I ended up increasing the bypass air from .110" to .125" because I thought it just needed more air. Even with this it only runs and idles well when I leave out the APT plug which causes a decent vacuum leak. Right now the power piston rod is sitting on top of the APT. Is this right? I also have the APT only screwed out about 2 turns, again making me think that maybe I got this wrong.

One last question, my kit came with 2 air horn gaskets. They appear to be the same with the exception of thickness. One is about .050" and the other is .032". I used the thicker gasket but was curious if this is correct.

Al

429bbf:
it goes on top . its purpose it to control how far the needles go in the jet when you have full vacumn pulling the metering rods down . i think your float level is set to high. I'm not saying 9/32 is not correct  .i would never argue with cliffs knowledge he's worked on more carb then iv seen.any idea what your fuel pressure is?i don't know how accurate you got your float set but i would lower it a tad and try it. if the fuel is to high it can act like it has a plugged vent. one thing you can try . its a little home school but it might help find your problem . if you have a rubber hose on the fuel supply some where try taking a vise grip and kinking it shut slowly while its idling . as you slow down the fuel see if it starts to idle better.fwiw

429bbf:
forgot about the gasket question the thick one is for folks with warped air horn . you can use ether i prefer the thin one if everything is nice and flat. the problem is lots of folks when there carb starts seeping fuel they crank the bolts down tighter and cause more problem down the road . the bolts should only torque max. 18.lbs hth

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