bad carb luck!
Thread Starter
Intermediate
Joined: Jul 2014
Posts: 42
Likes: 0
bad carb luck!
have a 79' Vette, she failed smog. I was told the carb is too lean and that is why my nox are up. well I had this car 3 years. This is my third Quadrajet. Current carb is a nos Quadrajet rebuild by Holley or called Holley II. Thing runs fine, better than the old carbs. I am sick of dumping money on parts that do not last. I wanna stay stock but who sells decent rebuilds? I do not wanna go Edelbrock and change all that stuff out. I just want a stock carb that works and not for 500.00. Am I asking too much? This carb thing is getting really old! I welcome any suggestions. Thanks, Steve
Racer
Joined: Jun 2015
Posts: 315
Likes: 20
From: Vasteras, Sweden
Send this guy an email, he rebuilt my Quadrajet, runs like clockwork!
He has been doing this for 30 years and have customers in US that shipped the carb for rebuild, lives in Sweden.
kentsqjet@hotmail.com
He has been doing this for 30 years and have customers in US that shipped the carb for rebuild, lives in Sweden.
kentsqjet@hotmail.com
Race Director
Joined: May 2006
Posts: 18,620
Likes: 2,553
1. Your state doesn't have emissions exemptions for cars older than 25 years?
2. What test is performed, idle emissions only or at various engine speeds? If idle speed only adjust the idle mixture screws.
3. Too lean a mixture can be also caused by a vacuum leak in a hose, may have nothing to do with the carburetor.
4. A bad EGR valve will also cause high NOX readings.
2. What test is performed, idle emissions only or at various engine speeds? If idle speed only adjust the idle mixture screws.
3. Too lean a mixture can be also caused by a vacuum leak in a hose, may have nothing to do with the carburetor.
4. A bad EGR valve will also cause high NOX readings.
Last edited by MelWff; Jul 8, 2015 at 11:26 AM.
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
1. Your state doesn't have emissions exemptions for cars older than 25 years?
2. What test is performed, idle emissions only or at various engine speeds? If idle speed only adjust the idle mixture screws.
3. Too lean a mixture can be also caused by a vacuum leak in a hose, may have nothing to do with the carburetor.
4. A bad EGR valve will also cause high NOX readings.
2. What test is performed, idle emissions only or at various engine speeds? If idle speed only adjust the idle mixture screws.
3. Too lean a mixture can be also caused by a vacuum leak in a hose, may have nothing to do with the carburetor.
4. A bad EGR valve will also cause high NOX readings.
Ask a shop to tweek carb, timing etc with 3 gas analyzer!
Last edited by mikem350; Jul 8, 2015 at 02:33 PM.
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Tech Contributor
Joined: Aug 1999
Posts: 14,356
Likes: 6,330
From: At my Bar drinking and wrenching in Lafayette Colorado
The Holley reman Q-Jets are exceptionally bad - I've never seen Q-Jets hacked worse than those built by Holley. The lean problem is typical of the Holley builds - they set the APT far too low, and often use jet/rod combinations that produce extreme lean conditions that will cause you to fail emissions. You're best off finding a used, original, unmolested carb and having it built correctly. Good, used rebuildable Q-Jets are available on eBay for under $100.
Racer
Joined: Jun 2015
Posts: 315
Likes: 20
From: Vasteras, Sweden
The Holley reman Q-Jets are exceptionally bad - I've never seen Q-Jets hacked worse than those built by Holley. The lean problem is typical of the Holley builds - they set the APT far too low, and often use jet/rod combinations that produce extreme lean conditions that will cause you to fail emissions. You're best off finding a used, original, unmolested carb and having it built correctly. Good, used rebuildable Q-Jets are available on eBay for under $100.
As i said in a previous post, Kent in Sweden is a Q-jet wizard!
Thread Starter
Intermediate
Joined: Jul 2014
Posts: 42
Likes: 0
The Holley reman Q-Jets are exceptionally bad - I've never seen Q-Jets hacked worse than those built by Holley. The lean problem is typical of the Holley builds - they set the APT far too low, and often use jet/rod combinations that produce extreme lean conditions that will cause you to fail emissions. You're best off finding a used, original, unmolested carb and having it built correctly. Good, used rebuildable Q-Jets are available on eBay for under $100.
Thread Starter
Intermediate
Joined: Jul 2014
Posts: 42
Likes: 0
So for the other members giving me input, this is the deal, the egr is new. I suspect the cat is bad due to running too lean too long, I am getting a deal one one today. Once I fix this I am sure she will pass but the carb nightmare continues. As far as smog goes, it failed the 25 mph test with high hc and nox. Mechanic stated lean carb is the problem. Since it is an old stock rebuild by Holley I don't think it is worth messing with at this point. I wanna get a good one, slap it in and be happy. Then I will take the Holley and have that one built properly and kept as a spare in my closet. California, 1975 and on you have to smog forever. They even make the test harder with this pressure test thing with the gas tank now. What a load of bull. So that is where I am at.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
So for the other members giving me input, this is the deal, the egr is new. I suspect the cat is bad due to running too lean too long, I am getting a deal one one today. Once I fix this I am sure she will pass but the carb nightmare continues. As far as smog goes, it failed the 25 mph test with high hc and nox. Mechanic stated lean carb is the problem. Since it is an old stock rebuild by Holley I don't think it is worth messing with at this point. I wanna get a good one, slap it in and be happy. Then I will take the Holley and have that one built properly and kept as a spare in my closet. California, 1975 and on you have to smog forever. They even make the test harder with this pressure test thing with the gas tank now. What a load of bull. So that is where I am at.
Wanna drive it up to the San Jose area?
Thread Starter
Intermediate
Joined: Jul 2014
Posts: 42
Likes: 0
had a new cat installed. the old one was clogged plus it had a lot of what looked like white sand in it, like from a charcoal bbq. car passed smog. the bad is I have a leak with the evaporate system that now caused it fail again and I screwed up and set the timing a little high. So sick of this. I hope to persuade Lars to take one of my carbs. I cannot afford to do the edelbrock transformation. ah sooooooo much fun. I will try to reply to posts asap but I cannot log in via facebook on my phone. I have to use my work computer.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
had a new cat installed. the old one was clogged plus it had a lot of what looked like white sand in it, like from a charcoal bbq. car passed smog. the bad is I have a leak with the evaporate system that now caused it fail again and I screwed up and set the timing a little high. So sick of this. I hope to persuade Lars to take one of my carbs. I cannot afford to do the edelbrock transformation. ah sooooooo much fun. I will try to reply to posts asap but I cannot log in via facebook on my phone. I have to use my work computer.
Burning Brakes
Joined: Mar 2014
Posts: 904
Likes: 46
From: Crestline CA
Seems like you failed the evap system pressure test. This test puts a slight amount of pressure in the fuel tank and measures the leak down rate. Parts included in this test is the fuel tank, fuel cap and all hoses up to the charcoal canister. Like Shark said, hopefully the problem can be repaired by replacing the easy to access vapor lines/hoses under the hood.