They were different. The Powerglide version in '53 had hydraulic lifters and a fully pressurized lubrication system, but those with manual tranny got solid lifters. In 1953 cars the solid-lifter version had 123 hp for standard transmissions and the hydraulic-lifter version had 136 hp (the Blue Flame) for Powerglide use. Here's a Wiki link that spells out the whole story - Chevrolet straight-6 engine - Wikipedia, the free encyclopedia