Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

17057253 carb not idling or revving

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Cliff Ruggles:
A good ported source directly to the vacuum advance would always do exactly what it needs to.  No timing at idle/coasting, and FULL timing from the advance right off idle, light throttle cruising, etc.....Cliff

Seff:
I'll try that. Got it idling lower by adjusting the right screw. >.>

Seff:
I checked, the DVCS connects to ported vacuum, so the result is the same, I think.

She starts and idles very well now - doesn't smell fat like she used to when idling and warming up. Tried to adjust the ATP via tip-in, but without a tach I'm having a hard time hearing those 50-100 RPM rises or drops. I'll see if I can get one.

Seff:
Alright, I found a tach and got my idle speeds right. My choke works well, and it drops to lower revs when it should. Timing is 24 at idle for an aftermarket HEI with the vacuum disconnected.

I want to adjust my APT, but I'm unsure if tightening or loosening the screw will lean the part throttle mixture. Seems such a simple thing, but I'm not sure. Logic tells me that tightening the APT will lean it out, since that allows the main rods to go further into the jets. Is this correct? The reason I'm doubting it is that my mileage got worse after I tightened it the first time around.

Cliff Ruggles:
24 degrees timing at idle is WAY to much.  Most engines will like around 8-12 degrees.  Some really low compressin engines with big cams in them may want a bit more, around 14-18 degrees, but 24 degrees is too much, and the total timing will be too high at full throttle.....Cliff

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