4 barrel
Thread Starter
Cruising
Joined: Jan 2009
Posts: 13
Likes: 0
From: Gardner Ma.
4 barrel
i have a 1969 350/350 4 speed with a edelbrock performer series carb and intake came with car. When i get on it in first and second it bogs until the 4 barrel kicks in . it seems like the 4 barrel is not kicking in fast enough . Checked timing ,plugs,wires cap rotor changed to electronic ignition. Not sure what to do. please any help would be appreciated new to the corvette world. thank you again
Scott
Scott
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
That's what most believe; that the q-jet bog is caused by the secondaries not opening fast enough. But in fact, the opposite is likely the cause; the secondary "air valves" are opening too fast. (I'm speaking of the air valves which are the big butterflies you see on the top of the carb on the secondary side).
There's an adjustment that regulates the opening of the secondary air valves located on the end of the air valve shaft, on the passeger's side. You need a 3/32" (I think) allen wrench and a small screwdriver.
Do a search on this site for details and how to adjust. If you can't find the instructions, get back with me, I'll walk you through it.
Good luck!
There's an adjustment that regulates the opening of the secondary air valves located on the end of the air valve shaft, on the passeger's side. You need a 3/32" (I think) allen wrench and a small screwdriver.
Do a search on this site for details and how to adjust. If you can't find the instructions, get back with me, I'll walk you through it.
Good luck!
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
The Performer uses a different system than the Q-Jet. It's quick and easy to tune.
Be *sure* your timing curve is set right before looking at the carb. Also be sure that you're getting WOT when the throttle is to the floor - have someone look down the primaries to verify.
Here's the instructions:
http://www.edelbrock.com/automotive_...ers_manual.pdf
And here's the tuning kit:
http://www.summitracing.com/parts/EDL-1486/
Note that my experience with these carbs has been that bogs come from too LIGHT springs vs. too heavy - Start with a stiff spring and work back.
Be *sure* your timing curve is set right before looking at the carb. Also be sure that you're getting WOT when the throttle is to the floor - have someone look down the primaries to verify.
Here's the instructions:
http://www.edelbrock.com/automotive_...ers_manual.pdf
And here's the tuning kit:
http://www.summitracing.com/parts/EDL-1486/
Note that my experience with these carbs has been that bogs come from too LIGHT springs vs. too heavy - Start with a stiff spring and work back.
Last edited by billla; Aug 4, 2009 at 10:26 PM.
Thread Starter
Cruising
Joined: Jan 2009
Posts: 13
Likes: 0
From: Gardner Ma.
4barrel
Thank you for the info I will try and tune it myself. Also somebody told me that these performer carbs have a tendency to have a bog on low end and i should switch to a holley 650/670 what do you guys think. just trying to cover all bases instead of spending unecessary money. I will say i love this forum thanks guys. Oh and the qjet no big deal i still appreciate your time.
Scott
Scott
Melting Slicks
Joined: Jun 2009
Posts: 2,709
Likes: 3
From: Savannah GA
You can probably get the Edelbrock to work nicely. The design is cribbed from the Carter carbs as used on the mighty Mopars back in the day... a 426 Hemi 'Cuda came factory equipped with a carb of very similar design; they were a formidable engine!
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Any properly sized, properly tuned and properly functioning carb will deliver the same driveability, fuel economy and performance within a few percentage points. I've installed hundreds of carbs, and I can tell you is that they all have their unique advantages and disadvantages for a particular installation - but they can all be made to work, and work well.
I've got an Edelbrock Performer carb and intake on my '72 C-10 with a 355 that makes about 400 HP...and after tuning it runs like a top. There's no bog, but as noted I did need to move to stiffer springs.
There are a lot of "holy wars" about one brand vs. another - but it's all
and it's usually driven by folks that just haven't taken the time to learn how to tune a particular carb.
I've got an Edelbrock Performer carb and intake on my '72 C-10 with a 355 that makes about 400 HP...and after tuning it runs like a top. There's no bog, but as noted I did need to move to stiffer springs.
There are a lot of "holy wars" about one brand vs. another - but it's all
and it's usually driven by folks that just haven't taken the time to learn how to tune a particular carb.
Last edited by billla; Aug 6, 2009 at 01:47 AM.
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Race Director
Joined: Aug 2004
Posts: 10,628
Likes: 132
From: Duvall, WA
Specifically, the problem with the Edelbrock AFB is that they have no adjustment to the secondary airflap for the opening rate, so it's not possible to set them up precisely for the power to weight ratio of the car. You might get lucky and have the right combination for the carb, but if not, the carb will never work correctly. Three different well known carb shops told me this when I was running an E carb. The Edelbrock Q-Jet on my Corvette, however, runs great. It's too bad they're not still making these.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
We'll agree to disagree
Yes, there's a secondary air valve but it's very different than the Q-Jet and I have seen no issues at all with bogging with properly tuned Performers.
Yes, there's a secondary air valve but it's very different than the Q-Jet and I have seen no issues at all with bogging with properly tuned Performers.
Thread Starter
Cruising
Joined: Jan 2009
Posts: 13
Likes: 0
From: Gardner Ma.
Okay waiting for the tuning kit for the edelbrock. All though i am still hering from guys at cruise nights that I need to put a 650/670 holley on my car. Does anybody know what the cfm of the original q jet that will tell me alot. And what do u guys think of upgrading my coil to a high performance for better spark what do ya think let me know just want to wake my car up a little. thank u again for all your help
Scott
Scott
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
CFM of the original Q-Jet is 780 CFM 
Folks recommend what they know.
An upgraded coil won't add any power. More capable coils extend the RPM range of the ignition system, but this doesn't really come into play until 5000+ RPM. An HEI upgrade is the best money you can spend on a GEN I, and coupled with an MSD box that's about as good as you need until you start making > 1.2 HP/CID...
Folks recommend what they know.
An upgraded coil won't add any power. More capable coils extend the RPM range of the ignition system, but this doesn't really come into play until 5000+ RPM. An HEI upgrade is the best money you can spend on a GEN I, and coupled with an MSD box that's about as good as you need until you start making > 1.2 HP/CID...
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
You can have a lean bog and a rich bog. A lean bog will almost always produce a backfire. A rich bog is just a lazy engine response. It would be important to know which you are dealing with when working toward a solution.
As for a different carb curing your ills...maybe, maybe not. It would depend upon the new carb attending to what shortcoming your dealing with. It pays to verify everything else is up to snuff before throwing money at the problem.
And, yes, the Carter/Edelbrock air valve secondary on the Performer carb leaves a lot to be desired from a tuning standpoint. It's just a counter-weighted air door. To tune the secondary opening rate you have to either add or remove weight from the counterbalance. How much in either direction is anyone's guess. A Q-jet is the easiest to tune since it's a matter of turning a screw to change spring tension. A Holley is a just matter of changing the vacuum motor spring. The Edelbrock Thunder series features an easily tunable secondary and is the one I'd consider if I wanted to use the E carb.
As for a different carb curing your ills...maybe, maybe not. It would depend upon the new carb attending to what shortcoming your dealing with. It pays to verify everything else is up to snuff before throwing money at the problem.
And, yes, the Carter/Edelbrock air valve secondary on the Performer carb leaves a lot to be desired from a tuning standpoint. It's just a counter-weighted air door. To tune the secondary opening rate you have to either add or remove weight from the counterbalance. How much in either direction is anyone's guess. A Q-jet is the easiest to tune since it's a matter of turning a screw to change spring tension. A Holley is a just matter of changing the vacuum motor spring. The Edelbrock Thunder series features an easily tunable secondary and is the one I'd consider if I wanted to use the E carb.
