Q: I have a Holley 800 cfm double pumper carburetor on the 454 in my 1970 Impala. The carburetor worked fine when I first installed it. But after the car spent six months in the garage, the engine dies when I go around a corner or when under normal to hard braking. At regular and high speeds the engine runs fine. Also, the engine dies when I set the idle higher than 900 rpm. What should I do to correct the problem?

ls4 454 in the engine bay of a 1970 chevy impala

A: It sounds like you need to do a major carb cleaning. After sitting so long, the fuel in the carburetor has evaporated, leaving a nasty residue which can cause all sorts of driveability problems. We suggest tearing the Holley down for a thorough inspection and cleaning. You may need to clean the rest of the fuel system as well.

Once the carb and fuel system are clean, turn your attention to the float levels in the fuel bowls. It sounds like fuel is flooding into the carburetor when you stop or make a turn, causing the engine to die. The secondary float is probably the culprit, but we recommend setting both float levels, just to be sure.

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