1970 - 1973 Corvette: Service Bulletin: Engine Overheat
Subject: Engine Overheat
Model and Year: 1970 - 1973 Corvettes with 454 Cu. In. Engines and Air Conditioning
Source: Chevrolet Dealer Service Technical Bulletin
Bulletin Number: 73-T-28, Section VI
Date: May 14, 1973
TO: ALL CHEVROLET DEALERS
Engine overheat may be encountered on some 1970-1973 Corvettes equipped with the 454 cu. in. engine and air conditioning during high ambient temperatures when operated in heavy traffic. This condition is due to the limited amount of air flowing through the radiator at low vehicle speeds or during periods of extended idle.
To improve low speed cooling, an additional grille panel lower extension was installed in 1973 Corvettes produced after Vehicle Identification Number 1Z37Z3S410722. This extension, Part Number 336176, may be installed as illustrated on page 2 of this bulletin on early 1973 Corvettes only .
In addition, a flex fan that provides increased air flow through the radiator has been released for service use on any 1970-1973 Corvette with 454 cu. in. engine and air conditioning. This fan replaces the original fan and fan clutch assembly and may be ordered in a kit, Part Number 6260480, that includes the necessary attaching parts. When using the flex fan, an increase in fan noise may be noticed under some driving conditions.