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. There is absolutely no reason to rebuild a set of OEM castings when you can buy a lighter, higher flowing and more detonation resistant cylinder head for less money from us!