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1957 - 1958 Corvette: Service Bulletin: Fuel Economy Drop - Rochester Fuel Injection Service Update

Model and Year: 1957 - 1958 Corvette
Source: Chevrolet Central Office Technical Service bulletin
Bulletin Number: DR #329
Section: VIm
Date: November 21, 1957


Progressive and gradual lowering of Fuel Economy on units equipped with #7014800 Fuel Injection may be due to partial restriction of the .030" venturi signal bleed hole in the air meter.

A dirt build up at this point gradually reduces the amount of signal bleed off, resulting in a progressively stronger venturi signal and increased enrichment.

The following procedure is recommended for cleaning the bleed hole.  (Reference 1958 Passenger Car Shop Manual, Page 10-74, Figure 136).

  1. Remove air cleaner assembly. 
  2. Remove four (4) screws holding air meter diffuser cone and remove diffuser cone only.  Do not remove venturi ring.
  3. Locate bleed hole on the interior surface of the air horn which is positioned on the horizontal centerline, on the rear side of the interior wall, approximately " in from the air cleaner attaching surface.
  4. Insert a .030" wire at approximately 45o to the surface to clean out the hole.
  5. Install diffuser cone and air cleaner assembly.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.

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