Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Trouble Tuning Inexperienced

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huntincowboy:
Hi everyone, got one of Cliff's SR kits for my 17084226 carb that I'm putting on a mild 460 ford in an f250 with Comp 252H cam, mildly ported & polished heads, long headers, and an HEI distributor.

Finally got everything in and plumbed and did the break in, carb idles ok and as long as I'm just sitting, it will rev smoothly. Drove it out of the shop to clean up and as soon as it get's loaded up it has a bad backfire in the exhaust that only gets worse when you give it pedal. I knew it needed tuned so I went to start tuning the carb up and I'm having no effect from the mixture screws, I can screw them all the way down on one side and it doesn't stumble at all. It's drawing right around 14-15 in Hg at idle around 800 rpm. I had initial timing set at 12* but backed down 10* after thinking that may help (it didn't).

I think it's running pretty rich, but that's just a guess, not very experienced with carbs in general and this is my first quadrajet. I have a holley regulator giving it a steady 5psi from an electric fuel pump that is the stock in tank style for an 86 f250 w/460.

My jets are a 75 with 50C rods and the secondary rods are DA's.

Do I possibly have too much jet/rod or does it sound like another issue? I have the float set at 1/4" and other than that and Cliff's SR kit, everything else is "stock". Also, there are no vacuum leaks that I can find, if that helps.

Cliff Ruggles:
During the rebuild did you remove the idle tubes or at least run a small wire thru them to clean them?

Did you verify the power piston hanger arms are level and EXACTLY even.

How many turns up from seated is the APT screw?

huntincowboy:
I cleaned the carb in an ultrasonic cleaner, but did not remove or run a small wire through the tubes. The piston arms seemed level but I didn't check them with any tool to verify exactness. What would be the recommended way to check? I left the apt screw alone

huntincowboy:
Ok I got the carb pulled and checked the apt adjustment, it was about 2-3/4 turns out. I have some wire I'll run through the idle tubes to check them. Still not sure how to exactly check eveness of the power piston arms, but they're not visibly uneven.

Cliff Ruggles:
Pull the metering rod tips together under the piston to verify they are exactly the same.

I'd raise the APT some and leave the plug off over it until you are done fine tuning or tap it for a set-screw so you can make changes without removing the airhorn.

Are you running vacuum advance at idle?

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