The Speedmaster FE heads are a perfect upgrade to their heavy and bulky stock counterparts. Not only do you get more performance out of the box than OEM heads, our heads are significantly lighter since they are made of _Gravity Die Cast_ aluminum. As another benefit, you can run higher compression with aluminum heads before the onset of power robbing detonation. Assembled with the finest premium components to provide your engine with optimal airflow for maximum engine performance Improved power throughout the rpm range for greater throttle response and top-end horsepower