Chevrolet by the Numbers: 1970-75
Fig. 3-7. Brand new for the 1970 model year was the 400 engine block. It was similar to the 350, but with a different bore and stroke. As a result, most of the internal parts were new, including crankshaft, pistons, rings, and rods. Head gaskets were not interchangeable, due to the water jacket holes shown above on the 400.