changed carburator from original 2 edelbrock. starts fine. runs bad/ 350/


Asked by Jun 28, 2013 at 08:09 AM about the 1968 Pontiac Le Mans

Question type: Maintenance & Repair

automatic transmision, when i try 2 drive car runs wery bad , nd dies.. whats a problem?

9 Answers


Did you adjust the air fuel mixture?

1 out of 1 people think this is helpful.

Tom is right- the adjustin' of the carb is a zen exercise- you must turn the little adjustin' screws until the car's aura is just the right color- also make sure all your vacuum hoses are connected and where they are s'posta be

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there is a stove kit, heat riser, butterfly valve and blend door that all must be working in harmony for cold starts~...once up to temperature- we can check the operation of these devices and THEN turn the screws on the front of the carburetor to "tune it into" performance~

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Sounds like a major vacuum leak...I'd use silicone rubber hoses, tho expensive never degrade or crack and leak vacuum~


trying still adjus, Screwin in and out dosnt hepl. still same sh. t and black smoke. hoses are fine. no leak. '.:) svitchet bach 2 old one -goes fine again. put brand new one problem coms back.

1 out of 1 people think this is helpful.

ok- let's back up- this carb is new out of the box? It will have to be jetted and the float level will have to be set- the black smoke is unburnt fuel- too much gas pouring into the engine

did you forget the vacuum advance line on the distributor? the black smoke tells me there's incomplete combustion...did you set the timing to 7degrees Before TDC...think that's where you want to be on this engine.~


Do you have a repair manual ? You need one to get the right specs for proper adjustments . Chevy 350 or Pontiac ?


Did you get the correct Edelbrock carburetor for your engine? They have different sizes (air flow, measured in CFM) as well as different styles. They have both the spread bore Q-Jet, made by Carter, which is a bolt on replacement for the Quadrajet, plus the square bore of the kind that Ford used, made by Weber. Make sure all the vacuum lines are connected properly and that any open vacuum ports are properly capped. I would also talk to the Edelbrock tech support people, and make sure you have the correct jets and metering rods for your engine and how you use it. A strictly city car needs different metering rods and jets than one used on the highway a lot. Also, have you adjusted the idle mixture correctly, as that sets the base line mixture for the metering rods. Make sure that both adjustment screws are in sync, i.e. turned out the same number of turns. Having a significant difference in the air/fuel mixture between the two sides will cause strange tings indeed to happen.

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