@vanditch1: For decades, the Chevy 400 small-block was the black sheep of the family. Hot rodders pulled them out of trucks and big sedans and threw them aside in favor of the 350. Today, the same engine is one of the most wanted small-block blocks around. Few engines have ever had such a complete change of reputation. Chevrolet introduced the 400 around 1970, as emissions rules got tighter and heavy cars needed more torque without the size and weight of a big-block. Engineers pushed the small-block about as far as it could go. They opened the bore to 4.125 inches and gave it a 3.75 inch stroke, the longest ever used in a production small-block. To fit those big bores into the same basic block, the cylinders were cast siamese style, touching each other with no coolant passages between them. That decision created the 400’s quirks. Without coolant between the cylinders, the engine was prone to running hot, especially in cars with tired radiators and poor maintenance. Chevrolet added special steam holes in the block and heads to help release trapped steam, which meant that regular small-block heads could not simply be bolted on. The 400 was also externally balanced, so it needed its own crankshaft, balancer and flexplate, breaking the small-block’s famous parts interchangeability. It went into heavy cars like the Caprice and Monte Carlo, station wagons and trucks, and by 1976 it had disappeared from most Chevy cars, lingering in trucks until the end of the decade. What hurt the 400 back then makes it valuable now. Those big bores and thick crank journals are perfect for building big displacement small-blocks. With modern cooling, light internals and good aftermarket heads, stroker builds of 406, 421 and even 434 cubic inches can make well over 500 horsepower with torque that feels like a big-block. Companies like Dart and World Products even build new 400-style blocks with thicker walls and better cooling.

vanditch

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Sunday 08 November 2026 02:50:53 GMT