Here's why:
* Aluminum blocks were not common in the era of the 427: The 427 engine was primarily used in the 1960s, a time when cast iron blocks were the standard for high-performance engines.
* GM's first aluminum blocks: General Motors (GM), Chevrolet's parent company, only introduced aluminum blocks to their high-performance cars in the 1990s, starting with the Corvette.
While there are aftermarket companies that produce aluminum blocks for Chevy engines, these were not made by Chevrolet themselves.
