Carburetor help

[Lorence]

Have a Edelbrock 650 on my charger. 383 stock build with a period hi perf intake.  All is good except for if I'm at idle and floor the gas it will cough and die.  Is this a lack of fuel from the carb pump?  Any advice will be good thanks. 

[XH29N0G]

This is difficult to tell.  It could be.  How is your ignition?  Is it electronic, or points?

When you say cough and die, does it backfire?  If it backfires through the carb it could be what you suggest.  My point about ignition is I started working on carb when I was first starting and then found my problem was the ignition.  Once that was done, I could figure out the carb. 

[Lorence]

Electronic ignition.

[Lorence]

Only will happen in gear not in park.  Will give a cough but if i get off pedal right after it will stay running.  Runs good otherwise. Idles good no leaks. 

[XH29N0G]

I have not worked with the edelbrock carburetors but there are folks on here who will know and will be able to help.  The electronic ignition helps.  My issues were with a points ignition.

If you do not have enough of a pump shot, you will stall and spit.  You might even backfire out of the carburetor.  I would think that you should be able to see if you get an accelerator pump shot by looking into the primaries after opening the choke and manually moving the throttle to activate it.  As I said I do not know much about these carburetors, but from what I see online, it looks like you can adjust the pump shot size which might make a difference. 

There are some other things.  IF the carburetor was not originally set up for this engine, it may also be that the main jets are not right.  That can also change how the carburetor behaves.  Further, if your right on the edge with idle settings, that can also change how it behaves.  (I have to set my idle a little rich from optimum to make it behave appropriately.  I also need the accelerator pump shot set up right and to have it come on as soon as the butterflies move.)

There will likely be some other people who chime in and will help. 

I know the edelbrocks can be made to run well.  Just don't have much experience with them myself.

[Lorence]

I'm getting a shot of fuel.  I'm thinking maybe not a big enough squirt.  I tried leaning out and making richer with rods and jets per chart but does not affect my issue.  Idle mixture is good and don't think that would be the issue.  Kinda stumped. 

[XH29N0G]

I have a few additional thoughts

Vacuum Leaks: One thing I have not yet run into (and therefore miss in my diagnosis) are vacuum leaks.  They can change the game.  You may want to rule them out first. 

Timing:  Also, where do you have your timing set?  This can have an effect on how the engine responds to the carburetor.

Finally, is this problem new?  In other words did it work before, but stopped working, or is it something that started with a new carburetor that you are working with.

After that.  Carburetors just meter fuel and if the mixture and amount is right, they behave well. It is important to be systematic if you are just starting down this road.  Let's see if someone signs on who knows these carburetors. I have really only worked with the Holley- style carburetors.  What I would with those do would be to make sure the idle is set to highest vacuum and then richen by a little (in my case 1/8 turn open on idle mixture screws after setting for max manifold vacuum at idle). After that I would set the main jets (high speed circuit) and then work down from there.  This is because (at least for the carburetors I have used) the main Jets can impact the transition and how much gas (and how fast) is needed from the accelerator pump.  After that I would work on the cruise.  and then the transition - your flooring it.

[Lorence]

Again no vacuum leaks. 

Already tried 2 stages leaner and 2 stages richer from stock calibration on rods and jets no change. 

Idle mixture seems good plus don't think that would be the culprit in this situation. 

Will try stronger rod spring later but don't think that's the solution. 

Also adjusted timing both ways few degrees and no change. 

[BSB67]

Too little information, many possible issues.

Is the carb new, or used?  What is the carbs history? Did it ever run right before? What is the car's history? Did it ever run right before?  What's changed.

1) Jet and rod size changes are not the problem.
2) Based on what you've posted so far, I'm not confident you could diagnose a vacuum leak
3) it could be timing.
4) it could be squiter.
5) it could be idle/transition circuits.

I would suggest a one time trial. Disconnect the distributor vacuum advance and set initial timing at 15°, and open the idle mixture screws one turn, and go for a test drive.  Report back.

[cdr]

What Russ said ^^^^^^^^^^^^^^^^^^^^^^^^  THIS^^^^^^^^^^^^^^^^

[Lorence]

Well all that did was make my car run worse at idle.  Just for reference ive had this car for 15 years.  This is the first ive had a hi perf intake and this carb on.  I just rebuilt carb prior to installation.  There are no vacuum leaks.  And yes i can figure the easy things out so a rod or jet or spring or timing are the first things I checked.  This is cars runs good unless i want to do a burnout then it dies.  There's a slight hiccup if I'm cruising and floor it.  Thanks.

[BSB67]

So, before the intake and rebuilt carb install, this problem did not exist. Correct?

Which change made it idle worse, timing or idle mixture?  How much did the idle vacuum change?  Did you take it for a ride?

What is your idle timing with the vacuum advance hooked up?  Is it connected to port or full vacuum?

What is you neutral and in gear idle rpm?

How did you determined no vacuum leak?

Which intake did you install?

What happens when you plug each IAB?