73-87 Chevy _ GMC Trucks > Fuel Systems and Drivability

Acceleration Problem After Pulls

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78C20Daws:
I have a stock 78 C20 with a 350 and a QuadraJet and factory HEI, and I have been having some issues with drivability after going 3/4 throttle or more. Truck starts, runs, and drives fine until I get on it. The first time getting on it goes well, but after that it bogs/chugs bad on light acceleration, especially from a stop. Changed the advance weights/springs/centerplate with no luck in solving the issue. Also if I leave it parked for a day then the problem seems to go away until I get on it again. Any ideas?


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bd:
As a fundamental step, validate the fuel pressure (~7 PSI), draw (>20" Hg), and volume (>1 Qt in 30 seconds of cranking) while the engine is cold.  Leave the pressure gauge connected and then monitor the fuel pressure when the symptoms arise.  Also, using an HEI spark tester...





...check the spark color and fullness when cold and then recheck it when the symptoms occur.

78C20Daws:

--- Quote from: bd on December 01, 2021, 01:26:38 pm ---As a fundamental step, validate the fuel pressure (~7 PSI), draw (>20" Hg), and volume (>1 Qt in 30 seconds of cranking) while the engine is cold.  Leave the pressure gauge connected and then monitor the fuel pressure when the symptoms arise.  Also, using an HEI spark tester...





...check the spark color and fullness when cold and then recheck it when the symptoms occur.

--- End quote ---
I will try that out tomorrow hopefully and see what I get, thanks for the reply!


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bd:
Another thing to try is to remove or loosen the fuel tank cap the next time the symptoms occur to see what happens.  This might reveal whether the tank is properly vented.

JohnnyPopper:
Sounds like it might be heat related.

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