Your first stop in engine identification is the VIN which will supply you with a code to identify the engine with which the vehicle was originally equipped. If you believe the engine is not original equipment for your vehicle, identification can be a little more difficult. Check the labels found on about the engine compartment (radiator shroud, power steering pump reservoir, air cleaner) for more clues. Your last resort is the often difficult to interpret engine codes.
All engines will have some engine build code attached on a label and usually stamped or laser cut into a machined pad on a portion of the block.
Engine identification number common locations:
4.3L engines: rear of cylinder block, below and behind the left cylinder head where the engines mates with the bell housing
4.8L engine: left side of block, just rear of center below the engine side cover
V8 gas engines: Front of the block just below the right cylinder head or on the left rear upper side of the block where the engine mates with the bell housing
V8 Diesel engines: front of the block between left cylinder head and thermostat housing and/or on the left rear of the block just behind the left cylinder head.
Some engines the number can also be found at the rear left of the block, just above the oil filter adapter or on the upper right, rear of the block.
Fig. Engine identification number locations 4.3L engines