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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 78Hawk on December 01, 2017, 07:54:01 am
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Hello All,
I’ve finally got the 78 C10 to start but idles ruff and when I give it gas it dies. Sometimes it will continue to run but not consistently. I’ve changed the fuel tank and pick up, coil, battery, distributor, ignition switch a the base of the steering column and had the carburetor rebuilt. What is the deal? The truck has a 454, Edelbrock intake and a Holley 4 barrel.
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The choke may be opening to soon would be my guess
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improper tune maybe? check for a vacuum leak and go from there.
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You need to check the accelerator pump discharge
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Hi 78 Hawk:
Sure sounds like carb problems. But, with all those replaced parts, have you verified the timing, dist advance features, initial idle mixture screw settings, and choke settings?
Regards,
Henry
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More info: Runs warm? Electric choke? Has it backfired thru the carb? Fuel filter and lines replaced with the tank?
Make sure there’s no open vacuum ports anywhere on the carb or manifold.
PVC hooked up and where?
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Yes it runs warm, electronic choke. Yes it back fired and actually shot fire from the carb.
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Holley’s are known for blowing power valves with intake backfires causing over rich idle mixtures causing rough idling.
Intake backfiring can be from incorrect timing, crossed up firing order, lean fuel mixture, vacuum leaks and also valve train problems.
Choke should open 1/8 to 3/16 when engine starts. A little either way makes a big difference in a cold engine.
Mileage on engine?