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Carter BBS Idleing too Fast
https://slantsix.org/forum/viewtopic.php?t=27592		 Page 1 of 1
Author:  killin5 [ Sun Mar 02, 2008 12:50 pm ]
Post subject:  Carter BBS Idleing too Fast
I just put a rebuilt carter BBS on my 63 valiant. I am now having problems getting the idle under control.

I can back out the idle adjustment and the it still idles high. Right now I can cruise at about 10 to 15 MPH at idle. Other that the idle adjustment screws, what else should I be adjusting here. This is the first time I have had a working carter carb on the car. Previously I had a Holley 1920.
Author:  SlantSixDan [ Sun Mar 02, 2008 12:58 pm ]
Post subject: 
There are two idle speed adjustment screws on the '61-up Carter BBS carbs. The one closest to the rear of the car is the one that sets your curb (warm/hot) idle speed. The one closest to the carburetor body itself sets your fast (cold) idle speed. Make sure you're adjusting the right one. If you are, and you can't get the idle speed under control, there's something else the matter (vacuum leak, improper gasket selection when rebuilding the carb, worn throttle shaft bushings, etc.)
Author:  killin5 [ Sun Mar 02, 2008 5:28 pm ]
Post subject: 
I looked it over and am thinking that I'm not getting enough tension on the throttle. I tried to shorten the throttle return spring, but didn't get it there. I can manually get it to where I need to, but it won't return. I didn't have a problem with this setup and the 1920 carb.

Is there a part number for the correct spring?
Author:  killin5 [ Thu Mar 06, 2008 9:46 am ]
Post subject: 
Ok, so I changed out the spring and I am still having the issue. If I press on the idle assembly I can get the idle to drop, but it does not do it without some force.

Is there something I can test with the bushings? I don't see anything holding it up. Is there anything inside the carb (adjustments, blockage) that would be causing this. I'm fairly sure I used the right gaskets.

I don't believe there is a vacuum leak. Which vacuum line would cause this?

Also, the screw that holds the fast idle cam on has a rubber bushing on it. It does not cover the entire shaft. Am I missing some other spacer?
Author:  gato [ Thu Mar 06, 2008 10:17 am ]
Post subject: 
i ask this having never seen a BBS carb. is the geometry of the throttle linkage identicle betwwen the BBS and the holley?
when u return the throttle to proper position by hand, will it stay there on its own, or does is return to the wrong position?


D~~~!
Author:  killin5 [ Thu Mar 06, 2008 11:31 am ]
Post subject: 
It is the same and it does stay there. It just does not return once you give more throttle.
Author:  SlantSixDan [ Thu Mar 06, 2008 1:20 pm ]
Post subject: 
Disconnect the rod that connects your accelerator pedal to the carburetor -- just pull the hooked end out of the bushing in the carb lever. If the carb now reliably returns to idle, you need to reset the threaded adjustor(s) in your throttle linkage system - one at the top of the riser rod coming off the back of the accelerator pedal and connecting to the back of the rod that runs forward to the carburetor, and one like it on the firewall side (the latter found only on cars with automatic transmissions). The factory service manual has the adjustment procedures and specifications.

You mention it's a "rebuilt" BBS — where did you get it/who rebuilt it? If there's throttle shaft warp, particular kinds of wear at the throttle plate/throttle body junction, or the shaft's straight but the body was rebushed too tightly, you'll have this kind of won't-return-to-idle problem.
Author:  killin5 [ Thu Mar 06, 2008 4:19 pm ]
Post subject: 
I disconnected the rod and the idle was good. Connected it back and it sped up. So hopefully that adjustment will work.

I have the service manual so I'll look up that procedure.

I did the rebuild on the carb so I am a bit paranoid about it. It was my first rebuild. I had never used this carb before so its origins are sort of unknown, but it looked solid and complete.

I'll give the adjustment a try and let you know how it goes.
Author:  VDART [ Thu Mar 06, 2008 4:32 pm ]
Post subject: 
Since your carb idles better without linkage connected----You might want to check your throttle rod linkage bushings. The one mounted to the firewall might be causing your linkage to hang up.(worn bushing/sleeve)
See how the project creep gets ya!! Lawrence
Author:  SlantSixDan [ Thu Mar 06, 2008 4:49 pm ]
Post subject: 
Should be an easy fix. This kind of issue can be caused by something as simple as a new carb base gasket thicker than the old one! :shock: And I'd have much more confidence in a carb you rebuilt yourself, than in a "reman" unit from the parts store. Those are yucky.

The next thing I'd do would be to unsnap the trans kickdown rod (the one that connects to the bellcrank immediately in front of the firewall) and see if the idle return is good. If it is, that's where to focus primarily on your adjustment efforts. But it's not a bad idea to do both adjustments every 35 years or so, whether needed or not :lol:
Author:  killin5 [ Sat Mar 08, 2008 11:34 am ]
Post subject: 
Well that did it. I spent a lot of time worrying about something simple.

Thanks for your help. The valiant is running great now.

John
Author:  SlantSixDan [ Sat Mar 08, 2008 11:48 am ]
Post subject: 
Good show, glad you got your Valiant's idle simmered down.
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