* Specific engine: Different big-block Chevy engines (e.g., 454, 427) might have slightly different clearances due to manufacturing variations over the years.
* Bearing type: The type of bearing used (e.g., standard, performance) will influence the ideal clearance.
* Desired performance level: A street engine will have different clearance requirements than a high-performance engine.
* Condition of the block and crankshaft: Wear on these components will affect the required clearance.
Instead of a specific number, you should consult the engine's rebuild manual or a reputable engine builder. They'll provide the correct specifications for your specific engine and build. The manual will give you the ideal bearing clearance, which you can then compare to your plastigage reading.
Plastigage only gives you a *measurement* of the clearance. It's up to you to interpret that measurement against the *specified* clearance to determine if it's acceptable. A slightly off reading might be acceptable depending on the factors listed above, but a significantly large variance would indicate a problem.
