Cool, Calm, and Collected: PLM 4-2-1 Header & Skunk2 Alpha Radiator Install 1991 Honda Civic Si EF

Reuploaded due to an audio issue. In this video, I walk you through the full process of removing my old no name aftermarket header from my 1991 Honda Civic Si and upgrading it with two high-performance components: the PLM 4-1 Bisimoto Replica Header and the Skunk2 Alpha Half Size Radiator. The PLM (Private Label MFG) Bisimoto Replica Header is known for its aggressive 4-2-1 design, improving exhaust flow and delivering noticeable gains in horsepower and torque—especially in the higher RPM range. It’s a perfect fit for enthusiasts looking to enhance the performance and sound of their classic EF chassis. Paired with the header, I also install the Skunk2 Alpha Series Half Size Radiator, which offers efficient cooling in a compact package. Designed specifically for Honda applications, this radiator features high-quality aluminum construction, TIG-welded seams, and improved coolant flow to help maintain optimal engine temperatures during spirited driving or track days. Whether you're restoring, upgrading, or building a track-ready Civic, these two parts offer a solid combo of performance, durability, and value. Check out the full install process, hear the before/after sound difference, and get tips to make your installation smoother. Don’t forget to like, comment, and subscribe for more EF build content and upgrades! #PLMHeader #Skunk2Alpha #CivicSi #EFHonda #HondaCivic #D16 #D16A6 #D16Z6 #D16Y8 #D15 #D15B #D15B7 #1991Civic #Bisimoto #HeaderInstall #RadiatorUpgrade #HondaMods #EFBuild #JDMParts #CivicBuild #CarDIY #PerformanceUpgrades