1956 Corvette: Service Bulletin: Spark Plug Fouling - Idle Adjustment

Subject:   Spark Plug Fouling - Idle Adjustment
Model and Year:   1956 Corvette - Dual 4-Barrel - Carter Carburetor
Source:  Chevrolet Technical Service Bulletin
Bulletin No:  DR #258
Section:   VI
Date:   August 30, 1956


In cases where Spark Plugs are wet fouling on V-8 Engines used in 1956 Corvettes with dual 4-barrel carburetors being operated in Metropolitan Areas which put considerable limitation on their top speed, it may be necessary to install AC-46 Plugs to correct this condition.

AC-44 Plugs are to be furnished in production.

Range of plug should be tailored to the owner’s requirements:

AC-44  Extreme High Speed Driving

AC-44  Medium High Speed Driving

AC-45  City Driving and Normal Operation

AC-46  Metropolitan City Driving Under Heavy Traffic Conditions


To obtain a consistent idle speed setting on V-8 Engines equipped with Carter 4-Barrel Carburetors with regular or racing camshaft, proceed as follows:

Engine Number Suffix -

GH  Regular Camshaft
GU  Racing Camshaft

Article ID: 975
Created: October 25, 2014
Last Updated: October 25, 2014

Online URL: https://www.corvetteactioncenter.com/tech/knowledgebase/article/1956-corvette-service-bulletin-spark-plug-fouling-idle-adjustment-975.html