Carb issues

[resq302]

Well for the longest time now, I have been battling a back fire through the carb when I go from idle to wide open throttle.  It did not do this prior to the rebuilt of the carb.  I decided to take the stock carb off, Carter AVS 4615 SA, and replace it with one that I had on there before going the all stock route.  The one that is on there now is a Carter AFB Competition Series 9636 SA.  This carb makes the charger come alive and want to roast the rear tires.  It totally seems like a different car.  The problem with this carb is that sometimes it idles at 1200 rpms and then would drop down to 850 and then back up to around 1000 rpms.  This carb also has at idle a bunch of black smoke coming out the exhaust, obviously, too rich at idle.

What I would like to do is to keep the original carb on there as the car is all factory stock appearing but I want the performance out of the stock carb that I am getting out of the Carter AFB competition series.  I believe that both carbs are 625 cfm.  The engine that they are on is a 383 ci that was bored out .030 over and has a mopar purple stripe restoration cam.

Any help would be greatly appreciated as the stock carb I have had back fire a bunch of times and had the secondaries have a little fire brewing inside there once it backfired.  Needless to say, I shut down the car rather quickly after that to prevent any damage to the car.

Brian

[resq302]

One thing that has been done was that the primary jets were increased from .089 (stock) to .092.  The secondary jets are still at the factory setting of .092 as well.  Should the secondary jets be bigger than the primary jets?  If the secondary jets were not big enough, would that cause the back fire through the carb at wide open throttle?

[68 RT]

The rich idle may be a choke adjustment, is it manual or electric?  On my edelbrock, I was having the same problem. I changed the step up springs and rods. Also moved up one step on the primary jets. This solved the problem. I did not change the secondary jets. I would try the step up springs.

[resq302]

The stock carb is a thermostatic choke that goes into the intake manifold.  The aftermarket Carter Comp. Series one has an electric choke.  The choke on the Comp series one was wide open when it was running rich.

[68 RT]

If it runs rich at idle with choke open I would check idle mixture screws. You could have a high enough idle that it is lifting the metering rods because the vaccum is dropping. The eratic idle is most likely a vaccum leak.

[resq302]

Well, after soaking the disassembled carb in parts / carb cleaner for 12 hrs, I reassembled it with the next size up secondary jets and a larger accelerator pump squirter that Dick Katter sent me and installed it on the car last night.  The carb seems to run much better and idles perfectly smooth holding a steady 950-980 rpms.  The throttle response is much beter and it still has an occasional bog or sputter when I go from idle to wide open throttle but it is MUCH better than what it was before.  I currently have the accel. pump rod on the center hole of the arm and will try to readjust it and put it in the top hole which should give me more volume for a squirt out of the accelerator pump.

I'll keep everyone posted.

[1969chargerrtse]

Well, after soaking the disassembled carb in parts / carb cleaner for 12 hrs, I reassembled it with the next size up secondary jets and a larger accelerator pump squirter that Dick Katter sent me and installed it on the car last night.  The carb seems to run much better and idles perfectly smooth holding a steady 950-980 rpms.  The throttle response is much beter and it still has an occasional bog or sputter when I go from idle to wide open throttle but it is MUCH better than what it was before.  I currently have the accel. pump rod on the center hole of the arm and will try to readjust it and put it in the top hole which should give me more volume for a squirt out of the accelerator pump.

I'll keep everyone posted.

Maybe you can tweak the timing a hair, sometimes that can help in the bog from idle to full throttle issue?

[resq302]

Right now I think I am going to try the route of the accel pump rod linkage.  If that does not do it, I will try the route of tweaking the timing.

[firefighter3931]

Right now I think I am going to try the route of the accel pump rod linkage.  If that does not do it, I will try the route of tweaking the timing.

Brian, you are going down the right path. 

With 18* of base timing you are good....work on the accelerator pump tuning and increase the "shot" to eliminate the off idle bog/backfire. 



Ron