Needle seat question

[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

[Bigal442]

I'm going to take the carb back apart to look it over. I will check the float and maybe adjust a bit lower. I arrived at using 9/32" mainly based on the recipe in the book calling for 1/4". I doubt this is the real source of my problem since the largest issue is at WOT.

Another interesting point is that I tried throwing the old secondary rods back in there and it did not make a noticeable difference' still bucking at WOT. Keep in mind the old rods were very lean (DB).

[429bbf]

how does the car run with the secondaries tied shut? also my understanding pulling the apt plug is not a vacumn leak . it would act as a vent and should have no effect. someone correct me if I'm wrong. i can pull it on my carbs and it makes no difference.one last thing hows the timing and the distributor . are they all working properly. I've seen ignition timing act like carb problems. fwiw

[Bigal442]

I haven't tried running it with the secondaries tied shut.  I too was surprised that I could feel a good vacuum from the APT hole. I did pull the carb back apart and found a significant issue with one side of the primary rod hanger being bent upward. See picture below. They were straight but I had to pull the airhorn back apart and I suspect I bent it at that time. At a minimum the one side would have the rod much higher than the other. I also think it's possible that the rod came completely out of the jet based on how it was running.

I bent the hanger straight and the car now idles much better, even with the APT plug back in. Just for a test I took the APT plug out and it did not change anything and there was no longer any vacuum from the hole. I suspect this is normal.

In the end the car does idle and run better but it still is not quite there on full throttle. I also tried adjusting the tension on the air flaps. I did a test in which I tried 3/8 and 3/4 past the tension neutral point. It ran better set at 3/8. Not sure what this is telling me in terms of rich vs. lean.

As far as the timing... I believe it's set correctly but I do need to check it again. With this particular car (70 Vette with power steering idler pulley) it is super tough to see the mark on the balancer. I basically have to put my head about 6 inches from the fan blade. It also more work to even power up the timing light with the car battery behind the drivers seat. Last time I checked it was about 34 to 36 degrees all in at 2800rpms. I am also running manifold vacuum. I haven't spent too much time investigating the timing since digging into the carb since I have not moved the timing. I have only owned the car for just over a month.

Next step may have to be changing out plugs because they are pretty fouled. Hopefully I can finish tuning and make progress on the WOT performance.


Allen

[429bbf]

its nice to here when someone finds there problems .i think flap tension is very important but i think too many people try and fix other problems with it .in my experience the speed of my pull off was where i found most of my issues if the spring was set real close to motor specs.glad to here its getting closer.fwiw

[429bbf]

you couldn't pay me enough to change plugs on that if its anything like a 1981 vette.id like to stuff the engineer in the glove box that did that. fwiw

[Bigal442]

Yep, not looking forward to changing the plugs. Having headers and AC on the car won't help either. I might have to reach out to the Vette community for any tips or tricks before attempting.

Any chance those plugs will go back to "normal" over a period of driving after I get the fuel and ignition dialed in?

[429bbf]

when you get those plugs to clean up . let me know how you did it. ive never been able to get on to work properly once they had a lot of excess fuel.

[Bigal442]

It may be a while before the weather and the streets allow for more road testing. I was thinking I would replace one or two of the easy plugs and then see how they do after some miles before I go after all those harder to reach plugs. It sounds like some of them will be tough to get to. Some are accessed from below and some through the wheel openings along with some special tools.