* Specific engine build: The crankshaft, connecting rods, pistons, camshaft, and internal components all have different strength and durability limits. A stock, low-compression big block will have a much lower safe RPM than a highly modified, high-compression, race-prepped engine.
* Internal balancing: Internally balanced engines can generally handle higher RPMs than externally balanced ones.
* Lubrication system: The oil pump and oiling system's ability to maintain proper oil pressure at high RPMs is critical.
* Valvetrain: The valvetrain (springs, retainers, pushrods, etc.) must be strong enough to handle the high inertial forces at high RPMs.
While some heavily modified big blocks might briefly reach 7000 RPM or even higher in a controlled racing environment, a safe and reliable operating range for a reasonably built street big block would typically be closer to 5500-6500 RPM. Going beyond that consistently without significant modifications risks serious engine damage.
In short, there's no single answer; it's highly dependent on the specific engine's build and intended use.
