Quadrajet removal

[crazy charlie]

I have done manifolds,risers,remove and hang outdrive etc and dont consider myself too handy.i have zero experience with carbs and i think its time to get one of mine rebuilt or at least looked at.how easy/complicated is it to remove and reinstall....?? Or should i leave it to a pro?? Charlie

 

[Lou C]

I did my Q-Jet last summer, I THOUGHT it would be complex but in reality it is not much more complex than taking apart a Hollley 4bbl. The issues are, the Q-Jet has an accel pump roll pin that has to be driven back to release the accel pump lever, before you can remove the air horn, and there is the auto choke linkage on the other side, that also has to be removed. Then the air horn will come off. Next you have to carefully line up the power piston for the primary metering rods with the air horn gasket (a little tricky) and also line up the secondary metering rods in the jets when dropping the air horn back on after cleaning. The other issue is you need to really give it a good soak and use a real air compressor to blast out the idle emulsion tubes because they can clog and cause issues. Took me about 2.5 hrs the first time going slow. If you've done other carbs, I'd try it if not might want to use a pro....

 

[Scott Danforth]

to R & R - 4 nuts hold it down to the manifold. other than that, there is the choke and throttle cable.

 

[kenny nunez]

In addition to the previous posts, If you take the carburetor apart be real careful not to lose the power valve spring. I looks like a ball point pen spring and looks purple in color. It is under the primary metering rod mounting bracket.
When re-installing I always hold the throttle plates wide open when snugging down the mounting hardware. After the bolts are tight open and close the plates to be sure they are not binding.

 

[crazy charlie]

thanks guys ,I have no intentions of taking the carb apart.All i want to do is remove it to take it for a rebuild and reinstall when they are done with rebuild..Dont exactly trust myself though.

 

[Lou C]

Then all you have is the fuel line, throttle linkage on the port side and the choke rod on the starboard side, don't lose the little clip that holds the rod that is hooked up to the choke coil in place. When you remove the fuel line that goes into the big nut that holds the small filter in the front of the carb, use a big adjustable wrench to hold that big nut and use a brake line style wrench to avoid rounding off the flats on the fuel line fitting. This way only the fuel line unscrews from the big nut not the whole thing that retains the small fuel filter.

When you reinstall it, check the thick gasket on the manifold if it is deteriorated you might want to replace it. I like to thread the fuel line fitting into that big nut before tightening the mounting bolts because it allows you to move the carb slightly if needed to get the threads started without stripping anything.
Some have 4 bolts, 2 up front and 2 in the rear, some use 2 bolts up front and a stud and nut in the rear. DO NOT overtighten the bolts/nuts when reinstalling, that is what warps the air horn on Q-Jets.

After that you have to set the idle speed and idle mixture, check back for how to do that.

 

[crazy charlie]

THANKS LOU!! I was given a specific carb wrench for the "big nut" .Seems there is a small black tube under the big nut that is not letting me use the specific wrench.The amber tube in fron t of the housing is in the way too but i will heat it and pull it off.

 

[Lou C]

the amber tube is the overflow tube from the fuel pump. Don't heat it too much lol! see if you can read what's on this pic, might help.

 

[crazy charlie]

YEP THATS THE CARB.Cant keep engine running after idling for 10 or so seconds.Stays running if i pump the throttle.Sound like a rebuild or is there an adjustment I can try?

 

[Lou C]

You can try adjusting the idle mixture but usually that's a sign of needing a cleaning/rebuild. The Q-Jet idle mixture screws are in the front under the fuel filter housing area. Some use regular screws with a slot, some use an odd shaped end that requires a flex tool with an adapter that fits the end of the screws. Depending on the shape of the thermostat housing they can be tough to get at. Holleys are easier being right on the sides.

 

[crazy charlie]

I dont remember seeing any but will take a closer look.Thanks again
!!

 

[crazy charlie]

The carb filter removal does not involve any reverse threading correct?? I had large nut/housing wrenched and fuel ine with brake line wrench and it wasnt moving.Pulling/holding housing with my right hand and pushing pipe wrench with my left .I was not comfortable feeling like i may have been forcing soemthing.

 

[Bondo]

The carb filter removal does not involve any reverse threading correct??

Nope,..... Both are righty tighty, lefty loosey,....

 

[kenny nunez]

All the threads are right hand. I have had some that no matter how good the tool is and patience the flare nut rounds off and you have to either cut the line close to the nut or put a pipe wrench to it. By cutting the line close to the nut there is usually enough of the line left to re-flare the line with a good flaring tool that double flares the line.

 

[crazy charlie]

Hmmm,i didnt think of that..??

 

[Lou C]

Ok here’s what I’d do...loosen all 4 mounting bolts so the carb is not solidly bolted down and it can move a bit. Sometimes due to the way the fuel line was bent it can hold the fitting in a bind. By loosening the mounting bolts it can relieve the bind and allow you to unscrew the fitting. I’ve had mine off 3/4 times over the years and never had a problem but leaving the carb loose helps a lot..

same thing if you have to replace a mechanical fuel pump; the fuel line fittings will line up easier and thread in easily if it’s not bolted solidly to the block. Put the bolts in and tighten them enough to hold it but not so tight that it can’t move...

 

[jimmbo]

YEP THATS THE CARB.Cant keep engine running after idling for 10 or so seconds.Stays running if i pump the throttle.Sound like a rebuild or is there an adjustment I can try?

Sounds like dirt/gum/varnish somewhere in the Idle circuit. Tubing Wrenches should be used on the fuel line fitting, prevents rounding the hexs off.

The Carb is easier to take apart and put back together if you remove the secondary Metering rods prior to removal of the air horn, a small screw holds the hanger they are suspended from

The Q-jet, while probably the most sophisticated Carb ever mass produced, isn't too hard to clean up and rebuild. I took my first Q-jet apart 40 years ago last month, and have did a few dozen more over the years. While it doesn't have the Mystique of of a Holley Double Pumper, it is an excellent carb

 

[Lou C]

Agreed on the Q-Jet, I think it is superior to the Weber/Edelbrock and Holley carbs, the issue now is that since they haven't been built since 1990 there are few good cores that haven't been altered/messed up by people who don't know what they are doing. It would be nice if someone could re-produce them, after all the modern Vortec carb intake manifold (4bbl version) is a spreadbore, made for a Q-Jet style carb. I hear Sierra was making a copy of the Q-Jet but no idea if they are any good.

 

[Luv2fish36]

Setting the floats correctly is the part you have to really pay attention to.