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1957 Corvette: Service Bulletin: Automatic Choke Piston Inoperative Due to Carbon Deposits

Subject: Automatic Choke Piston Inoperative Due to Carbon Deposits
Model and Year: 1957 - 265 & 283 CU. IN. V-8 Engines
Source: Chevrolet Service Bulletin
Bulletin Number: DR #278, Section VI
Date: April 29, 1957


A new more durable Exhaust Manifold Choke Heat Tube has been released for production and service to provide a tube more resistant to heat.

In instances where the Automatic Choke Piston becomes inoperative due to carbon deposits, the Exhaust manifold Choke Heat Tube should be checked for leaks or damage.


Remove Carburetor Choke Pipe Assembly and shine a light into the lower end of choke tube to see if carbon deposits are visible from upper end.


Leaking or damaged tubes should be removed by driving tube out with a 5/16" diameter drift from the top of manifold. In some cases where the tube has become badly rusted or corroded in place, it may be necessary to remove the manifold from the engine to facilitate replacement.

Care must be taken not to elongate holes in manifold.


New tubes should be replaced from the bottom of manifold by driving until upper end of tube is flush with manifold and then staked securely in two places at bottom end.


 Number RequiredDescriptionPart No.
Old 1 Exhaust Manifold Choke Heat Tube 3739717
New 1 Exhaust Manifold Choke Heat Tube 3747292


EL Harrig
Manager, Service and Mechanical Department

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.

© Copyright General Motors Corporation. All Rights Reserved.


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