DNA Motoring HDS-BBC396-572 Stainless Steel Exhaust Header Manifold Made of high quality T-304 Stainless Steel with computerized mandrel-bends for strength and durability i.e. Maximizing smoothest high exhaust air flow rate High performance 2-piece 4-1 racing Spec. Design (8-2-1) TIG welded CNC machine flanges Matching V-Band clamps and 3.5" flanges to customize for turbo Inlet: 2.25"/ outlet: 3.4" ID (V-Band)/ forward or top mount configuration Color: Metallic Materials:Stainless Steel Surface Finish: Polished Inlet / Outlet: 2.25&#034; / 3.4&#034; Fits 65-95 Chevrolet Big Block 366 / 396 / 402 / 427 / 454 / 502 / 572Cu. In. Engines Direct Bolt-On Installation, Requires No Modification. Professional Installation is Highly Recommended (No Instruction Included). Headers are one of the easiest bolt-on accessories you can use to improve an engine&#039;s performance. The goal of headers is to make it easier for the engine to push exhaust gases out of the cylinders. When you look at the four-stroke cycle in How Car Engines Work, you can see that the engine produces all of its power during the power stroke. The gasoline in the cylinder burns and expands during this stroke, generating power. The other three strokes are necessary evils required to make the power stroke possible. If these three strokes consume power, they are a drain on the engine. Our professional technicians do heavy research and development in testing car applications and fitments for our products. We also do testing on the strength, durability, as well as longevity of the material in order to make sure when the product arrives at the consumers end that its ready to go without worries.