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Post Info TOPIC: Stumble on acceleration


Veteran Member

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Posts: 54
Date:
Stumble on acceleration


Hi all,
Still have a stumble,
I tried disconnecting the vacuum advance on the pertronix ignition to see if it helped with stumble but it remained the same plus 2 backfires.
Next I tried 80 plus miles with a sea foam additive plus a bit of chevron hi-test and it remained the same.
The plugs are good along with new air cleaner and fuel filter.
Im thinking its a new carb rebuild. I had it rebuild 4 years ago and figured it was pretty bullet proof but it is old and may be past its prime,
Ill do a tear down and have a lookie loo.
Unless there are any other good thoughts out there?

Thanks

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Canadian Poncho Superstar!

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Posts: 4453
Date:

When you say stumble, do you mean its runs along fine but hesitates/stumbles when you try to speed up? If your carb kit had a black rubber/plastic accelerator pump, they dont last long on ethanol. A leather one will work fine forever almost.

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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC.
1963- Pontiac top selling car in Canada

Mahone Bay, NS Still not old enough to need an automatic



Veteran Member

Status: Offline
Posts: 54
Date:

Hi,
Yes when I speed up,
Bur mostly on hill climbs , it does have the black rubber accelerator pump.
Ill have to take a look,
Thanks

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Canadian Poncho Superstar!

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Posts: 4453
Date:

See what NAPA have for this carb, they used to sell the accelerator pump separately.

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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC.
1963- Pontiac top selling car in Canada

Mahone Bay, NS Still not old enough to need an automatic

MC


Canadian Poncho Superstar!

Status: Offline
Posts: 7264
Date:

FWIW, I'll back up Don to say that anytime I've had a stumble on acceleration with a carbureted engine, the accelerator pump is the first thing I look at and almost always solved the problem.



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Poncho Master!

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Posts: 1801
Date:

Like the others, accelerator pump, almost every time. (Once it was due to a bad set of points/poor spark, but its been decades since I messed points on a car).
I have heard that a back fire can blow the accelerator pump. Ive never experienced it myself, (and cant remember which carb it related to) but the solution is the same change the accelerator pump, then set it to get that shot in early.

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Veteran Member

Status: Offline
Posts: 54
Date:

Hi yall
Update:
So Ive had another carb fella do a tear down on the carb. Since time is in short supply.
He replaced the accelerator pump and readjusted the floats level, they were set a little lower to help with the slight weeping I was having before . It may have been starving for fuel. Anyways it definitely is running way way better but still having a slight stumble but much reduced. I will drive it for a bit and see if it levels off, but may need a little more mousing around .
Thanks for all your input
Bob

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