Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Rebuilt Carb-Still Gassy
Schurkey:
--- Quote from: batsong on January 20, 2009, 10:52:40 AM ---The richness is so excessive (I can smell strong exhaust going down the highway with the windows closed) that I'm thinking that there is something simple that I'm missing.
--- End quote ---
First Guess: You have holes (Rust holes in the underbody or trunk; missing grommets; broken plastic A/C--Heater box; missing drain hose in the A/C box...and there's lots more possibilities) in the passenger compartment that are allowing fumes in. Seal the holes.
Second Guess: You didn't do yourself any favors by going to all the trouble to drill throttle blades and modify the carb in other ways--but not bothering to un-seal the idle mixture screws.
batsong:
It's an old car. There are a lot of places the exhaust can leak in.. If I smelled normal exhaust in the cabin, I would not worry. I've tried to plug them up temporarily until I move to that area in earnest
I didn't cut out the idle screws because I've haven't found them to have any effect on this problem when I've had another Q-jet on (they always seem to go back to the way I found them). I was trying something new. I have extra throttle plates, I figured no harm done.
All of this is so I can learn and have fun with an old car. I am trying to improve efficiency and performance so I can drive it to work, but obviously, if there something wrong with the engine, I don't want to drive it for fear of damaging it. My plugs are normal, and my carb, whether inadvertently or not, seem to be set up o.k. The oil is thin and gassy, so I think fuel has been walking out along the fuel pump arm. I'm worried I might wash out my rings.
That's my defense. I came to this forum not for idle reasons, but because I've exhausted all other possibilities.
Thanks, Gabe
Cliff Ruggles:
Setting up any quadrajet exactly for an application is like making a batch of chocolate chip cookies. If you leave out the chocolate chips, don't expect to make good cookies.
I would go into the book, identify your carburetor exactly, and the location of the idle airbleeds, main airbleeds, idle tube, idle down channel, idle bypass air, etc.
Install a set of solid primary throttle plates, pick a recipe that corresponds to your application, and custom tune every area of the carburetor exactly to the specifications listed.
Every "recipe" is street, dyno, and track tested. The only need to vary much from the recipes would the altitude or climate where you live. If you send me a note, I can help with that area if needed.
It's quite rare to even find a q-jet with the idle taper proof caps still in place. Most were removed by dealerships under warrantee due to customer complaints. Even with the caps removed, the holes under the mixture screws were so tiny on most models that even with the screws backed out 6-8 turns they couldn't get enough idle fuel to the engine!
Also keep in mind that a lean carburetor will "stink" ten times more than one running correctly or even slightly rich. If you do NOT put enough fuel in suspension for complete combustion, the by-product is some really "stinky" exhaust fumes, as tons of unburnt particles exit the exhaust pipes. This often fools a lot of tuners into thinking the carburetor is way too rich, when more times than not, it is way too lean......Cliff
batsong:
Thanks, Cliff, for the tips. That's cool about the lean mixture being stinky.
I feel bad because I probably should have waited before making any posts on this forum because my post is not really about setting up a carb, but instead about troubleshooting a nagging problem. I've had limited money and time and was basically trying to troubleshoot by doing quick stuff to various areas to see if anything made any difference. I intend on doing complete job on the carb, but it's only been about 5 days since I started, and the shop where I plan to cut out the mixture screws is 26 miles away. I am taking all of your suggestions to heart.
-Gabe
Cliff Ruggles:
Also keep in mind that getting good results involves exact precision with tuning, stick with the "recipes" exactly and use the one that meets your needs.
Also, it is manditory to use good parts. Over the counter kits are still using up old stock. They lack many parts required to do a complete/correct rebuild, and many of the parts will NOT last long in contact with ethonal and/or modern fuel blends.....Cliff
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