The first aluminum radiator (3147516) was used on 1960 high-performance (270/290Hp) Corvettes. This radiator had an aluminum overflow tank attached to the top and is therefore commonly referred to as a "top tank". This tank was not a pressured expansion tank. The first version featured a smooth flat top and had no plastic coolant-level viewing plug. The radiator was unpainted and used a 13-psi pressure cap. In the middle of the 1960 production year, five ribs were added to the top of the tank for added strength. Shortly after that change, the plastic coolant-level sight hole was added, creating yet a third version of the radiator. The radiator part number changed to 3151116 for the early 1961 (270/315) high performance Corvettes and was used up to Vin. number 1700. The only change made to the radiator was an aluminum nipple and coupling was added to the assembly. None of the original production versions were painted. Only GM service parts were painted black.