Doug Thorley Headers THY-364Y-C Chevy and GMC 1973-1987

Thorley headers are designed to outflow your stock exhaust manifolds. These headers increase gas mileage and give your engine more horsepower across the entire rpm range. The Tri-Y configuration builds the most power in the middle rpm range, which is great for towing and steep grades. To make these headers last, Thorley made them out of durable 14-gauge mild steel with 3/8 in. thick flanges and 5/16 in. collector rings. To prevent leaks, these headers have an O-ring welded into the flange, in addition to the high-temperature gasket provided. Unless otherwise noted, these headers are designed to fit the vehicle as it came from the manufacturer. This includes components like cylinder heads, chassis, steering, motor mounts, body mounts and bushings, etc. If your vehicle is using aftermarket components, parts from other applications, or custom altered parts, then it is the installer's responsibility to verify fitment. Header Style: Tri-Y Header Material: Steel Header Finish: Silver ceramic coated Primary Tube Diameter (in): 1 5/8 in. Collector Attachment: Stock flange Collector Diameter: 2.500 in. Tuned: No Primary Tube Gauge: 14-gauge Flange Style: Standard Flange Thickness (in): 3/8 in. Bolts/Studs Included: Yes Gaskets Included: Yes Reducers Included: No Y-Pipe Included: Yes Motor Mounts Included: No Transmission Mount Included: No Quantity: Sold as a kit. Drivetrain 4WD Power Steering Yes Power Brakes Yes Air Conditioning Yes Standard Transmission Column Shift Yes Standard Transmission Floor Shift Yes Automatic Transmission Column Shift Yes Automatic Transmission Floor Shift Yes Application Footnotes: 2 - Will fit with angle plug heads. 3 - This Thorley header is available from stock with metallic ceramic coating by adding a "-C" to the part number. However, all Thorley headers can be coated--call for price and availability. 6 - This header is available with standard 1/4 in. air injection fittings by adding an "-S" to the part number. 10 - Will require air conditioning bracket on models equipped with "long" style compressor (1988 and earlier). Specify A/C compressor mounting location. L/S bracket P/N 8506. R/S Bracket P/N 8506. 15 - This header is available with fittings to accommodate models with dual air injection pumps. These use 7/16 in. -18 fittings. This was installed on some 1984-92 small blocks and 1985-89 big blocks. To order, add a "-DA" to the end of the part number.