Weekend Projects
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
Weekend Projects
Next week I am off and I want to get the car running like a top. Right now my 64 327/300 runs ok, but sputters when I put the petal to the metal. Everything is stock except for an electronic fuel pump. I am thinking the secondaries on the carb aren't opening, or the fuel pump is not putting out enough pressure. Spark plugs were replaced a year ago.
How do I get the secondaries to open if they aren't? Is it as simple as reattaching some linkage?
Any other ideas?
Also, something is draining my battery (prolly something in my new stereo) so I am going with one of the knife style cut-off switches. That and a polish all the shiny stuff and vacuum of my new carpet and it should be ready to go.
How do I get the secondaries to open if they aren't? Is it as simple as reattaching some linkage?
Any other ideas?
Also, something is draining my battery (prolly something in my new stereo) so I am going with one of the knife style cut-off switches. That and a polish all the shiny stuff and vacuum of my new carpet and it should be ready to go.
Tech Contributor
Joined: May 2005
Posts: 15,576
Likes: 118
From: Conroe Texas
300 horse - that's a Carter AFB carb, correct?
First check that fuel comes out of the squirters the instant you operate the accelerator linkage. If you can move the linkage without fuel coming out, adjust the linkage first.
The secondaries open via engine vacuum provided the little lock-out arm is moving freely out of the way first. This little arm is on the driver's side of the carb.
First check that fuel comes out of the squirters the instant you operate the accelerator linkage. If you can move the linkage without fuel coming out, adjust the linkage first.
The secondaries open via engine vacuum provided the little lock-out arm is moving freely out of the way first. This little arm is on the driver's side of the carb.
Race Director
Joined: May 2006
Posts: 15,554
Likes: 555
From: Eagle, Idaho
Went to start my '54 a few weeks ago after sitting over winter and the gas went bad. Siphoned all the gas out, put in new gas and once the new gas reached the carbs it ran fine. I think the 10% alky stuff goes bad pretty fast.
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
300 horse - that's a Carter AFB carb, correct?
First check that fuel comes out of the squirters the instant you operate the accelerator linkage. If you can move the linkage without fuel coming out, adjust the linkage first.
The secondaries open via engine vacuum provided the little lock-out arm is moving freely out of the way first. This little arm is on the driver's side of the carb.
First check that fuel comes out of the squirters the instant you operate the accelerator linkage. If you can move the linkage without fuel coming out, adjust the linkage first.
The secondaries open via engine vacuum provided the little lock-out arm is moving freely out of the way first. This little arm is on the driver's side of the carb.
The lock out arm doesn't seem to be doing anything...What does it "lock out." Seems like something here is amiss, but I've never worked on a quadrajet before.
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
Fuel is not old. Drove the car a couple times this winter.
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
The fuel comes out fine when the accelerator is operated. The secondaries don't seem to open at all. They should open if you go from idle to full throttle instantly right?
The lock out arm doesn't seem to be doing anything...What does it "lock out." Seems like something here is amiss, but I've never worked on a quadrajet before.
The lock out arm doesn't seem to be doing anything...What does it "lock out." Seems like something here is amiss, but I've never worked on a quadrajet before.
Are you working on a Rochester Q-Jet, or a Carter AFB? Q-Jets were never used on pre-'68 Corvettes.
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Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
No, the secondaries won't open by revving it in the driveway - the engine has to be under load; the secondaries open based on the engine's demand for air, not just on throttle position.
Are you working on a Rochester Q-Jet, or a Carter AFB? Q-Jets were never used on pre-'68 Corvettes.
Are you working on a Rochester Q-Jet, or a Carter AFB? Q-Jets were never used on pre-'68 Corvettes.
And I thought the Carter was considered a q-jet, I didn't know Quadrajets were a "brand name."
Drifting
Joined: Jun 2009
Posts: 1,277
Likes: 275
From: Leo IN
Here is what a Rochester Quadrajet looks like
A Carter AFB:
A Carter WCFB:
A Quadrajet is a very different four barrel carburetor.
For C2 carbs, see:
http://corvette-world.com/corvette_1...arburetors.php
For grins and giggles, a Holley will look something like:
-- Joe
A Carter AFB:
A Carter WCFB:
A Quadrajet is a very different four barrel carburetor.
For C2 carbs, see:
http://corvette-world.com/corvette_1...arburetors.php
For grins and giggles, a Holley will look something like:
-- Joe
Last edited by out2kayak; Apr 8, 2012 at 10:18 AM.
Drifting
Joined: Jun 2009
Posts: 1,277
Likes: 275
From: Leo IN
Next week I am off and I want to get the car running like a top. Right now my 64 327/300 runs ok, but sputters when I put the petal to the metal. Everything is stock except for an electronic fuel pump. I am thinking the secondaries on the carb aren't opening, or the fuel pump is not putting out enough pressure. Spark plugs were replaced a year ago.
How do I get the secondaries to open if they aren't? Is it as simple as reattaching some linkage?
Any other ideas?
Also, something is draining my battery (prolly something in my new stereo) so I am going with one of the knife style cut-off switches. That and a polish all the shiny stuff and vacuum of my new carpet and it should be ready to go.
How do I get the secondaries to open if they aren't? Is it as simple as reattaching some linkage?
Any other ideas?
Also, something is draining my battery (prolly something in my new stereo) so I am going with one of the knife style cut-off switches. That and a polish all the shiny stuff and vacuum of my new carpet and it should be ready to go.
1. Fuel line pressure - check with a gauge such as: http://www.amazon.com/Aeromotive-156...3851268&sr=1-2. Cheap and cheerful.
2. If you have proper fuel pressure, check to see that when the linkage drives the carb from full closed to full open you see a healthy stream of fuel sprayed into the venturi (the engine does not need to be running for this check -- just full pressure from the electric fuel pump).
One thing that you don't identify is if the issue is when the vehicle is going from a dead stop or accelerated from cruise. Thoughts?
A bog from idle could be too much play on the throttle plate or the idle speed air screw is set incorrectly (depending on the carb you have).
A bog from cruise can be a bad timing advance mechanism or the secondaries opening too soon. The latter would be (depending on the carb) controlled by weights or a spring. If it's weights, I would seriously doubt that they are out of adjustment, but a spring can weaken with age.
How crusty is your carb? Does it need a good cleaning? When you did a tune up, did you do the points / condenser / cap / rotor / etc? Did you adjust the dwell with a dwell meter (and check to see if everything moved correctly)? After, did you adjust the timing?
Just some ideas...
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
First of all it is a Carter AFB.
The sputter is from both a standing start or cruise. With the accelerator pushed gradually, the car will travel throughout the rpm range just fine. But if I really slam the gas, it sputters, especially at 3500+.
The carb was totally rebuilt in 2010 by a reputable carb guy who has a vette with the exact same engine.
The timing and dwell were set by my father with timing gun and dwell meter. I will check the timing soon, but don't have the dwell meter.
The sputter is from both a standing start or cruise. With the accelerator pushed gradually, the car will travel throughout the rpm range just fine. But if I really slam the gas, it sputters, especially at 3500+.
The carb was totally rebuilt in 2010 by a reputable carb guy who has a vette with the exact same engine.
The timing and dwell were set by my father with timing gun and dwell meter. I will check the timing soon, but don't have the dwell meter.
Le Mans Master
Joined: Nov 2004
Posts: 5,254
Likes: 768
From: Waterford WI
The 3rd picture is the strangest looking WCFB I've seen. Looks much more like a Rochester 4-jet to me.
Here is what a Rochester Quadrajet looks like
A Carter AFB:
A Carter WCFB:
A Quadrajet is a very different four barrel carburetor.
For C2 carbs, see:
http://corvette-world.com/corvette_1...arburetors.php
For grins and giggles, a Holley will look something like:
-- Joe
A Carter AFB:
A Carter WCFB:
A Quadrajet is a very different four barrel carburetor.
For C2 carbs, see:
http://corvette-world.com/corvette_1...arburetors.php
For grins and giggles, a Holley will look something like:
-- Joe
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
First of all it is a Carter AFB.
The sputter is from both a standing start or cruise. With the accelerator pushed gradually, the car will travel throughout the rpm range just fine. But if I really slam the gas, it sputters, especially at 3500+.
The carb was totally rebuilt in 2010 by a reputable carb guy who has a vette with the exact same engine.
The timing and dwell were set by my father with timing gun and dwell meter. I will check the timing soon, but don't have the dwell meter.
The sputter is from both a standing start or cruise. With the accelerator pushed gradually, the car will travel throughout the rpm range just fine. But if I really slam the gas, it sputters, especially at 3500+.
The carb was totally rebuilt in 2010 by a reputable carb guy who has a vette with the exact same engine.
The timing and dwell were set by my father with timing gun and dwell meter. I will check the timing soon, but don't have the dwell meter.
as far as the miss or poor throttle response, sounds like an ignition problem to me or a vacuum leak at the carb base for starters....jmo....good luck...
Tech Contributor
Joined: May 2005
Posts: 15,576
Likes: 118
From: Conroe Texas
Secondary Lock Out
These photos are of the 3269S Carter AFB on my 62.
The lockout is hiding behind the silver idle/choke plate, here it is blocking the secondaries from being able to open:
And here I'm manually holding the lever out of the way so that if the engine were running the secondaries would be able to open under the proper conditions.
The lockout is hiding behind the silver idle/choke plate, here it is blocking the secondaries from being able to open:
And here I'm manually holding the lever out of the way so that if the engine were running the secondaries would be able to open under the proper conditions.
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 942
Likes: 3
From: Louisville KY
These photos are of the 3269S Carter AFB on my 62.
The lockout is hiding behind the silver idle/choke plate, here it is blocking the secondaries from being able to open:
And here I'm manually holding the lever out of the way so that if the engine were running the secondaries would be able to open under the proper conditions.
The lockout is hiding behind the silver idle/choke plate, here it is blocking the secondaries from being able to open:
And here I'm manually holding the lever out of the way so that if the engine were running the secondaries would be able to open under the proper conditions.
Last edited by Lou64; Apr 8, 2012 at 04:19 PM.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
they normally do not open too soon on an afb. the secondary air valve is counterweighted and open with air through the carb. the lock out prevents this until the choke is fully warmed up and open.....look for binding or stuck air valve or sticking lock out or sticking choke......
