Rochester Quadrajet Idle Circuit - Fix Your Idle Problems

[@johnbecker5213]

i've rebuilt/repaired/cleaned about 100 of these q-jets, the needle/seat and float are sure finicky , i use the enclosed needle/seat assembly (one piece) and they seem to work good for me, had trouble with the two piece ones with the wire due to all these new mechanical fuel pumps ,had two that had 4.5-5 psi and have had ten or more with anywhere from 9.5 to 17 psi the one piece needle and seat worked good (no flooding) up to about 10psi any higher had to use a regulator i don't use these for performance use them for economy get much better mileage than my holleys you have real good videos i watch them from time to time just to refresh my memory and see if i can learn something new thanks for taking the time to make these!!!!!

[@MikesCarburetor]

I appreciate the feedback. I would suggest a regulator on anything over 5 lbs. Too much of a chance of rich or flooding.

[@davidpotter7484]

I have a 67 to 76 tune up specifications book. SD-100. A factory manual, a book every dealer had. I bought several different years, up to 95. The earlier ones are better, the later ones were adjusted with tailpipe sniffer computers. Every single q-jet fuel air mixture screw settings are 4 turns out. Plus or minus 25 rpm, more or less. The 1 and a half turns, after contact, is the idle stop screw, initial setting. Not for adjusting idle speed. I drive a factory 85 with. Qjet # 17080213, full manifold vacuum carb and get 16.5 mpg, if i drive careful, on the highway, for the last 11 years. Its all very specific settings following the specific process, nothing arbitrary, or by ear.

[@Hsmith6921]

I couldn't see what he was pointing out because he was holding the part away from the camera instead of towards the camera.

[@billhayward2668]

I bought a rebuilt Q jet from rock auto #702 9207 and out of the box it ran very rich. Adjusting the idle mixture screws where no help. The float level was good. I installed a fuel pressure regulator and adjusted it down to the #2 and it ran better. I decided to take it a part and found that the power piston spring appears to be too short. It doesn't lift it at all. I looked for a carb kit that has the spring included ,wasn't able to find one. I found a number of springs in your store but I have no clue which one is correct. Any help would be greatly appreciated. Great video,thanks

[@budlesage3358]

Do you do rebuilds if I were to ship my QJet to you? Rough price range?

[@MikesCarburetor]

Sorry don't do any rebuilds anymore.

[@garyanderson4462]

Mike, what makes a quadrajet surge when driving

[@MikesCarburetor]

Look for any fuel restriction - check for kinks in the fuel line. Replace any fuel filters - There is usually one in the fuel inlet of the carburetor and often there will be an in-line fuel filter. Vacuum leak - Use spray carburetor cleaner and spray around the base of the carburetor and any vacuum lines. If the RPM smooths out, then you found the problem. There could also be a leak at the intake manifold. Check the float level. The power valve may be sticking. It needs to move up and down freely. Dirt in the system - take the top off the carburetor. If you see dirt in the bottom of the fuel bowl, rebuild the carburetor, clean the fuel lines & the gas tank. Main metering jet may be the wrong size. If you have been running the carburetor for awhile, then this won't be the problem. Jets don't wear out. Make sure the jets are not loose, or plugged.

[@garyanderson4462]

@@MikesCarburetor thank you Mike

[@ringgap]

are the butterfly screws staked on that one??

[@MikesCarburetor]

They usually are.

[@georgeh1650]

I need some advice if you don't mind. Have qjet gm350. Recently rebuilt. Runs great wot. Won't idle, idle fluctuating up and down, idling bout 900 to 1000. I've checked every thing. Not sure what to do. Thanks.

[@MikesCarburetor]

Please refer to this page for some ideas. Could be a lot of different things: www.carburetor-parts.com/quadrajet-rough-idle.html