1. Engine Block Design: The 1979 305 engine uses a different engine block design compared to the 1991 305 engine. The cylinder head bolt patterns, coolant passages, and other mounting features are not compatible between these two engines.
2. Combustion Chamber Configuration: The combustion chamber design of the 1979 and 1991 305 cylinder heads is different. The 1979 cylinder head has a larger combustion chamber volume compared to the 1991 cylinder head, which affects the engine's compression ratio and performance characteristics.
3. Intake and Exhaust Ports: The intake and exhaust port configurations on the 1979 and 1991 305 cylinder heads are not the same. The port sizes, shapes, and locations vary, making it difficult to match them up with the intake manifold and exhaust system of the 1991 engine.
4. Valve Train: There are differences in the valve train components between the 1979 and 1991 305 engines, such as the valve sizes, valve springs, and rocker arms. These components are designed specifically for each engine and may not be compatible when swapping cylinder heads.
Due to these significant differences, it is not recommended to use a 1979 Chevy 305 cylinder head on a 1991 305 engine. Compatibility issues may arise, leading to engine performance problems or even potential engine damage. If you need to replace the cylinder head on a 1991 305 engine, it's best to obtain a cylinder head specifically designed for that engine model to ensure proper fitment and functionality.
