1973-1977 C3 Radiator Expansion Tank Cap 340194, 345478 - OEM Number(s) (340194,345478)
Keep your Corvette’s cooling system factory-correct with the proper GM expansion tank cap.
For 1973, General Motors upgraded Corvette cooling by replacing earlier pressurized aluminum expansion tanks with a new non-pressurized plastic design. This correct GM radiator expansion tank cap matches the original 1973–early 1977 plastic surge tanks, restoring the look and performance intended by the factory. Manufactured in the proper translucent white plastic, this cap is GM Original Equipment and is sold individually for precise, reliable fitment.
Fits the Following Corvette Models:
Material/Finish
Dimensions
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Overall cap diameter: 2 1/4 in (57 mm)
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First outlet: 31/32 in (25 mm)
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Second outlet: 1/2 in (13 mm)
Features/Benefits
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GM Original Equipment, not an aftermarket substitute
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Correct fit for 1973–early 1977 Corvette plastic expansion tanks
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Proper translucent white finish replicates factory design
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Maintains correct cooling system function and authenticity
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Also fits 1974–1975 Camaro, 1974 Chevelle, 1974–1975 Nova, and 1973 Chevrolet Pickup Truck
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GM reference part numbers: 340194 and 345478
Because Details Matter
The cooling system is more than just function — it’s a piece of engineering evolution in Corvette history. Using the correct GM cap preserves not only performance but also the authenticity of your engine bay. Collectors know that every factory detail, even down to the translucent finish of a cap, adds value and pride to a true restoration. Because details matter when it comes to your Corvette.
Also known under these part numbers: (For reference only)
- 145125
- 18797
- 243111
- 25-120564-1
- 340194
- 345478
- 686420082354
- 8901