How can you tell what size truck motor have its a Chevy and the number is v1004trh supposed to be small block 400 it or not thank you?

The number "V1004TRH" doesn't directly correspond to a small-block Chevy 400 engine designation. Chevrolet's engine codes are more complex than that. The "V" likely refers to a V-type engine, but the rest of the code is not standard Chevy nomenclature for identifying engine displacement (like a 350 or 400).

To determine if it's a small-block 400, you'll need to find other identifying information on the engine itself:

* Casting numbers: Look for casting numbers on the engine block. These numbers are usually found on the block's side, near the front, and will definitively identify the engine. You'll need to cross-reference these numbers with a Chevy engine casting number database (easily found online).

* VIN number (Vehicle Identification Number): The vehicle's VIN will often indirectly reveal the engine. You can use online VIN decoders to get detailed specs, including engine type.

* Engine stamped information: Look for markings directly on the engine's valve covers, air cleaner, or other components. Sometimes, the engine displacement (e.g., "400") is stamped somewhere.

* Service records: If the truck has service records, the engine type should be clearly stated.

Without additional information besides "V1004TRH," it's impossible to confirm if it's a small-block 400 Chevy engine. The number provided doesn't align with typical Chevrolet engine identification schemes.