4:2:1 Tri-Y Headers

The Doug Thorley Headers THY-364Y-C features a 4:2:1 Tri-Y design, engineered to provide a significant power increase across the entire RPM range, making it an ideal street header. Constructed from durable 14-gauge mild steel with robust 3/8" thick flanges, these headers are built to last. The silver ceramic coating not only offers a sleek finish but also serves to reduce under-hood temperatures and protect the headers from corrosion. This header set includes all necessary hardware such as bolts and gaskets, along with reducers/adapters for installation. However, a Y-pipe is sold separately. The primary tube diameter is 1-5/8" with a 2-1/2" collector diameter and a 3-bolt flange collector attachment. Fitment is specific to 1973-1987 Chevrolet/GMC K1500 Pickup Truck, Suburban, Blazer, and Jimmy models, as well as 1973-1991 Chevrolet/GMC K2500 and K3500 Pickup Truck, Suburban, Blazer, and Jimmy models. Crucially, these headers are for 4WD models only and will not fit Heavy Duty, Big 10 Chassis, or Heavy Half models. They are compatible with coil spring front suspension and fit with straight or angle plug heads, but will not seal properly on D-port cylinder heads.