* Smaller Valves and Ports: 305 heads typically have smaller valves and combustion chambers, and smaller intake and exhaust ports compared to heads designed for a 327. This will restrict airflow, reducing the engine's ability to breathe efficiently, especially at higher RPMs. The 327, having a larger displacement, needs more airflow to perform optimally.
* Lower Flow Rates: The smaller ports and valves in 305 heads will lead to lower flow rates compared to heads designed for the 327. This directly translates to less power and potentially lower torque.
* Potential for Lower Compression Ratio: Depending on the specific heads used, you might end up with a lower compression ratio than what is optimal for the 327. This can reduce power and responsiveness.
In short, while it might be physically possible to bolt on 305 heads, the performance gains would be negligible, if any, and it's far more likely that you'll see a decrease in performance. It's much better to stick with heads designed specifically for the 327 or choose aftermarket performance heads optimized for a 327's displacement and potential.
