Carter BBD expertadvice needed

NWPT70

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Hi guys,

I am looking for expert advice from those of you who are familiar with the Carter BBD 2 barrel carburetors found on many of our beloved C bodies.

Previously In this thread thread -->>

Anyone else have minor hesitation/jerking at part throttle??

I was troubleshooting an at cruising surging issue on my 70 Newport that we believed to be an ignition issue but after I decided to swap carbs to a remanufactured unit I bought, the surging vanished! The car runs well now at all speeds and throttle with the reman BBD but the only quirk it has now is that if you rev the motor in park/nuetral anywhere say past 1200 rpm the revs take an extra second or 2 to settle down to base idle. I have the mixture screws set so it idles happy. This extra second or 2 of rev doesnt necessarily cause any driveability issues BUT i would like to get to the bottom of it because it never did this before and I can confidently say it's something with this new carb.

My thoughts so far...

Could the accelerator pump need breaking in or possibly set too high? (It is currently set for the middle hole on the linkage).

Could I have an internal fuel or air bleed somewhere ? Maybe faulty remanufacturing?

Vacuum leak somewhere? (the carb base gasket is tight)
 
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CBODY67

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Thanks for the update!

My experience has been that when the rpms don't quickly and linearly return to hot, base idle, it can be due to a vacuum leak somewhere, usually the base gasket. Do NOT over-tighten the hold-down nuts! Using an OEM-type thicker gasket, rather than the thin ones usually supplied, always has worked better for me.

Do re-check the torque on the hold-down nuts. As the gasket has a few hot/cold cycles, it can apparently shrink a small bit, which can cause what you describe. The thinner gasket can take multiple re-torqiues, too, over time. Which is why I went to an OEM thick gasket and the problem was solved.

Just my experiences,
CBODY67
 

Wildaugust

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Some other possibilities that could be an issue are the throttle return spring, sticking linkage, sticking throttle shaft or the throttle plates binding in the bores. Also, if there is some type of dashpot/solenoid keeping the revs from dropping, but I don't know if they would have one in that year.
 

NWPT70

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Thanks guys for the advice. I checked for air leaks around the base gasket and intake gasket using carb cleaner and I have detected no leaks.

While parked Ive checked the throttle linkage and shaft to see if its sticks but at a glance it doesn't appear to. However, I noticed on my most recent test drive that the throttle at 2 different instances stuck at around 2500 rpm. Both times simply revving the engine up a bit dislodged the stuck high idle. I am now suspecting the throttle plates may be binding intermittently as suggested. Just have to confirm this somehow..

(I guess I am paying the price for buying a bulk reman\off the shelf carb. I am going to try to let this be a learning experience working on these things. )
 

68PK21 440.6bbl

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Check your throttle shaft for wear, and don't just check it a one position, rotate it thru the whole range and see if you get wiggle anywhere. Lately I've come across someone that drives by I'll call 'stabbing on the pedal' not the usual cab/city driver of racing up to someones bumper and braking but press pedal, release and again stab repeatedly to maintain speed.
What are the feet too small? Legs too short (that's a possibility) <smh>
Someone that drives like that will wear out a tons of s#1t right quick.

.
 

NWPT70

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That's guys. Will be checking the throttle plates and base gasket tomorrow . Will report back with my findings.
 

NWPT70

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Turns out the screws for the base of the carburetor housing were not snug. Problem solved. Lesson learned. = Always check other people's work.
 
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