Chevrolet built the 1969 Nova SS with the L78 396, a 375-horsepower solid-lifter big block, and then left it out of every official sales brochure. Buyers had to know to ask for it by code. Enough of them did that it accounted for nearly a third of Nova SS production that year. Read on for what the engine really was, why Chevy stayed quiet, and how to tell a genuine car from a clone.