Q-jet gurus help!

[Blaster11]

Having some problems with the Q-jet on the Camaro so I am in the process of rebuilding it. The problem I am having is that it is excessively rich at idle, like can't be in the garage rich. after doing some reading I am leaning towards the spring for the needles is too strong compared to the vacuum. Sorry I don't have the vacuum reading right now , I took it apart and neglected to check first. The cam is a Comp 280 and the intake is an RPM if that helps.
Also has anyone ever sealed/replaced the two plugs in the bottom of the bowl, which are notorious for leaking, I was just wondering what your results were?

Trying to get it on the road after owning it for about four years so I can concentrate on the Firebird. I guess it's the ADD thing.:rotfl:

Thanks

[sporter]

I'm certainly no guru but I've had the same problem myself. That Comp 280 has 230 @ .050 and a lsa of 110 so its going to be a bit lopey and probably pull about 10-12" at idle. A lighter power piston spring will definitely help.

Do you run vacuum advance? Just hooking up my vacuum advance to manifold vacuum really helped my idle.

If the well plugs are leaking it will idle rich but the best indicator is if the fuel bowl is drained after the engine has shut down overnight.

Once you change the power piston spring, try to tune the carb for the highest vacuum at idle. You may find your idle air/fuel screws still have little or no effect on the idle mixture. If so, you probably need to increase the size of your idle air by-pass ports. I had to increase mine from .075" to about .155" to get the proper idle mix when I upgraded my cam. The idle air by-pass ports are located in your baseplate. Check the photos at the link for the location of the ports.

http://www.ponchopower.com/Carb_pics/carb_pics.html

A copy of Cliff's new book will really help you to set up your Q-jet for a high performance application.

http://www.cliffshighperformance.com/

Another good link with Q-jet info:
http://www.florida4x4.com/tech/quadrajet/index.php

Good luck.

[Blaster11]

Sporter,

Thanks for the reply, yes I am running a vacuum advance and yes it is hard to start after sitting for a while. Will the Edelbrock Q-jet parts like springs and metering rods work in a factory Q-jet?

Thanks for the links!

[69TAPoser]

As Sporter said, Cliff is the man when it comes to q-jets. He can be found over on the Performance Years forum:

http://forums.performanceyears.com/forums/

...You can usually find him in the Race section.

Phil

[sporter]

Yes, I use the Edelbrock calibration kit with my Q-jet. Just make sure you have the right kit to match your Q-jet. I think the cut-off is 1967-1974 uses kit #1991 and 1975 and later uses #1992.

[ls427ss]

the fuel wells on the main body are leaking fuel into the intake manifold. some kits have a ruber/foam type plug to install in the baseplate to stop this but do not work well. The best way to stop it is to use a fuel resistant epoxy on the bottom of the 2 fuel wells (marine tex works the best). Hard start hot (or flooded) is ALWAYS raw fuel entering the intake, and q-jets are famous for it. The springs can not cause a flood condition during starting, and will only affect driveability after started. Don't chase your tail fixing things that have nothing to do with raw fuel dripping into the intake on hot soak.

[Blaster11]

I think I will give Cliff a call tomorrow and order his book. I guess I will start looking for some good epoxy. Thanks for all the answers.

Bruce

[LowBuckX]

The well plugs that are notorious for leaking are the OLD style that look like freeze plugs knocked in. The newer type that you most likely have are aluminum spun in( friction welded) and normally will not leak.
A good test is to run the engine till warm then shut it off and take the bolts/nuts loose and place a sheet of paper bettween the carb and intake. You will see the fuel leak on the paper. Also if you take the base plate off and the reciver well is not wet or stained you are not leaking at the well plugs.

Id think your power piston spring is to stiff. not the well plugs.

Cliff is about 25 minutes from me and his carbs are the best you can get in a q-jet.

[Blaster11]

It is a 72 vintage carb and I believe the well plugs are leaking and the power spring is too stiff. If/when I get it back together I am going to try it first without the power spring and see how or if it will idle that is supposed to be one of the tests.

Bruce

[malibujason79]

to me it sounds like one or both of the primary rods is not in the jet. if you look in the carb from the top you can see the top of the hanger. use a thin screwdriver and see if it moves in and out of the jet freely.

[JEFFTATE]

Yes , the spring could be too firm ; or it could just be stretched out too far and it's holding the metering rods out of the jets too much.
Or the rods aren't in the jets , like malibujason was saying.

[Blaster11]

The carb is torn down for a good cleaning and get the gaskets replaced. I was hoping to get a hold of Cliff of Cliffs High Performance but have had no luck, I have tried email and calling but no luck. Was hoping to get some parts/recommendation from him on a good set up. I may just stick it back together and see how it is.

Bruce

[LowBuckX]

Cliff wrote a book that is redily available. Im sure he isnt going to offer up to much advice for a carb he did not build.

[Blaster11]

Since i couldn't get a hold of him I ordered the book, hopefully that will get here early next week. I think you guys are right it is the spring on the metering rods.

Bruce

[69keith]

Trash under the needle seat..

[Blaster11]

Talked to Cliff, of Cliffs performance, today about my problem, he seems to think and I don't disagree, that one of my problems is that I have too much cam for the compression. Throttle shafts are loose, too much spring for the needles, and the idle circuit is pretty out of whack for the combo, so.... I ordered his book last week and as soon as it arrives I am going to take a bunch of measurements and call him back so we can put the best combo available together. Cliff is a super guy to talk with and really knows these carbs inside and out. I will let you know as this progresses.

Bruce

[Skip Fix]

Cliff is a great guy and will definitely talk to you if you can catch him. The carb business has really grown and kept him busy.

[David Pozzi]

Another problem with Qjets is the floats absorb fuel and get heavy which raises the float level even though the setting is correct.

We have a heck of a time getting our farm pickups to pass bi-annual smog checks because of it. Also make sure your idle air restrictors are not plugged, this will cause a rich idle because fuel enters the engine in droplets instead of an air/fuel mix.

You can buy a cheap float scale to weigh the float, but just replacing it is pretty expedient. Weigh it right out of the carb, don't weigh it after it's dried out.

You can verify that the metering rods are fully down at idle by sticking a small piece of rod down the vent right above the metering rod hanger. Push down gently and see if it moves. DON'T push hard and bend the rods!!!
David

[LowBuckX]

If you paint the flaot with clear mail polish they will not absorb fuel. I prefer the brass floats.