Where is the oil sensor or pressure sending unit for a Chevy Big Block engine?

The location of the oil pressure sending unit on a Chevy Big Block engine varies slightly depending on the year and specific engine configuration (e.g., 396, 402, 427, 454). However, it's almost always located on the engine block itself, near the oil filter.

More specifically:

* Most common location: On the side of the engine block, relatively close to the oil filter, often near the distributor. It's usually a threaded fitting, sometimes with a single wire connection to the gauge.

* Less common, but possible: In some instances, particularly older or modified engines, it might be located on the oil pump itself.

To be absolutely certain, you should:

1. Consult a repair manual: A factory service manual specific to your year and engine model is the best resource. It will have diagrams and precise locations.

2. Refer to a parts diagram: Online parts stores (like AutoZone, Advance Auto Parts, etc.) often have diagrams you can browse by year and engine.

3. Visually inspect the engine: Once you've identified the general area, carefully look for a threaded fitting (usually 1/8 NPT) with a single wire connected. This is the most likely candidate.

Remember to be careful when working near hot engines and use appropriate safety precautions. If you're unsure, it's best to seek assistance from a qualified mechanic.