Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
7029207 transition too rich
Kenth:
All the 9202 Qjets i have notes on has the same size upper and lower idle airbleeds as the 9207´s, .079"-.081" uppers and .062"-63" lower bleeds.
Down channels in both are in the .051"-.053" range.
Only difference in idle/lowspeed circuit is the idle tube size,
Larger airbleeds equals leaner mixture, just like smaller idle tubes.
bob69:
So I've made some changes but the carb still runs rich at low rpms. The idle tube was changed from .037 to .035. With no other changes, the afr's changed from around 13.2 to around 13.6. Not as much as I was hoping.
Next, the float level was changed from .250 to .375 in the hope that lowering the float level would lean out the carb. I did not see much of a change in the transition rpms. However the afr's did get leaner some in the 1600+ rpms. The most notable change was in heavy accelerations. Performance felt down.
I checked the secondary hanger to see is the secondaries were too high. They were within specs. I did notice the transfer slots were exposed around 60% at idle. Not sure if this is normal for a 7029207.
Any other suggestions?
Kenth:
Next step i would open idle bypass air from .073" to .095"-.100".
bob69:
Kenth, the original IAB was .098. It was opened to .110. The afr's on the initial test were around 14.1 in the 1300-1700 rpm range. Exactly what I was looking for. The idle screw was closed 1/2 to 3/4 turn. The idle needles were adjusted leaner - 1/4 turn. The IAB holes were .110 with a smaller .098 restriction at the end of the hole. Very easy to drill out.
Now I have a new problem to solve.
After driving around a bit, I did a medium hard acceleration. Afterwards the afrs dropped to the previous 12.9 to 13.2 range for cruze and idle. By chance there was road work up ahead causing a 1 mile backup. Never got on the gas as we crepted along. The afrs kepted getting leaner. After about five minutes the afrs were in the mid 14 range. Idle was deteriorating.
After the road work, the afrs stayed in the low 14 range while driving slow. But as soon as I gave it some pedal the afrs went back to the low 13 range. After that the afrs would move around a bit. In the low 13s at times, then changing to the high 13s at times.
Any ideas as to what is causing the afrs to change like this.
quadrajam:
Sounds temperature related. Was it hot weather then? Carb
getting hot??
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