Engine stumble with light pedal action - HELP!
Thread Starter
Racer
Joined: Dec 2003
Posts: 399
Likes: 0
From: Haslet,Texas
Engine stumble with light pedal action - HELP!
Ok, here is the problem. I get on the gas, and the engine runs and pulls fine. But the second I get into a good cruise and am barely pushing the gas to keep a constant speed, I get a bucking action. It happens at any speed, but only when I am barely pushing the pedal. It's like the engine is either cutting in and out or surging. It's annoying the hell out of me. 
I read this thread - http://forums.corvetteforum.com/showthread.php?t=879769 - and I wish I could try some of the above solutions, but I'm using an Edelbrock 600 Performer. Any ideas for a solution using this type of carb?
I read this thread - http://forums.corvetteforum.com/showthread.php?t=879769 - and I wish I could try some of the above solutions, but I'm using an Edelbrock 600 Performer. Any ideas for a solution using this type of carb?
Thread Starter
Racer
Joined: Dec 2003
Posts: 399
Likes: 0
From: Haslet,Texas
Have you done anything to your distributor in regards to advance? This can be a sign of too much combined vacuum and mechanical advance.
The Edelbrock carbs are easy to tune. How familiar are you with changing rods/jet/springs?
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
First thing if you don't have the book - down load it off their site.
Ensure that your vacuum advance is to the ported connection on the carb - not full vacuum.
The idea behind them is simple. You have a two step rod that goes up and down inside the jet with the amount of engine vacuum. The rod is a restriction to flow.
High vacuum like cruise down the freeway the rod is down so the thick part is restricting fuel leaning out the mixture for best gas mileage.
When you push on the gas vacuum goes away the rod lifts to the smaller diameter step on the rod making the mixture richer for power.
Changing the rod spring determines how fast the rod moves with changes in engine vacuum.
They are a wonderful carb and I used them for over 10 years and tune friend's Edelbrocks even today
Ensure that your vacuum advance is to the ported connection on the carb - not full vacuum.
The idea behind them is simple. You have a two step rod that goes up and down inside the jet with the amount of engine vacuum. The rod is a restriction to flow.
High vacuum like cruise down the freeway the rod is down so the thick part is restricting fuel leaning out the mixture for best gas mileage.
When you push on the gas vacuum goes away the rod lifts to the smaller diameter step on the rod making the mixture richer for power.
Changing the rod spring determines how fast the rod moves with changes in engine vacuum.
They are a wonderful carb and I used them for over 10 years and tune friend's Edelbrocks even today
Thread Starter
Racer
Joined: Dec 2003
Posts: 399
Likes: 0
From: Haslet,Texas
Try disconnecting the vacuum advance for a short test run and see if you have the same problem.
Ensure that your vacuum advance is to the ported connection on the carb - not full vacuum.
Changing the rod spring determines how fast the rod moves with changes in engine vacuum.
http://store.summitracing.com/partde...25135%20300585
For only 5 bucks, hopefully someone local has it.
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Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
IF your timing is OK:
My first thought was that your primary circuit is too lean at cruise. Since you have one of those Edelbrock Carter AFB clones, you'll have to get the procedure for swapping out rods and jets elsewhere.
Plenty of AFB folks around here, though. Good luck.
My first thought was that your primary circuit is too lean at cruise. Since you have one of those Edelbrock Carter AFB clones, you'll have to get the procedure for swapping out rods and jets elsewhere.
Plenty of AFB folks around here, though. Good luck.
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Originally Posted by Bobchad
Have you done anything to your distributor in regards to advance? This can be a sign of too much combined vacuum and mechanical advance.
If you haven't checked your timing there's no way to know (for you or for us) if it's the problem or not.
