Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Needle seat question

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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

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