There's no single definitive answer to the stock cylinder compression for a 5.7L V8 Pontiac Tempest. Pontiac didn't use a 5.7L V8 in the Tempest. The Tempest, particularly in the years it was offered (generally the 1960s and early 1970s), used a variety of V8 engines, but none were 5.7 liters (350 cubic inches). The most common V8 displacements in that era's Tempests were smaller, like the 326 or 400 cubic inch engines.
To find the correct compression ratio, you need to know the *exact* year and model of the Pontiac Tempest and the specific engine code (often found on a sticker on the engine block or in owner's manuals). Once you have that information, you can look up the factory specifications in a repair manual or online resources specializing in Pontiac information.
