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THY-303Y-C / 1973-91 GM / Chevrolet 396-454 BBC Pickup / Suburban / Blazer (2wd) Tri-Y Headers

Availability: out of stock

Header style
Weld up
Carb EO #
Yes: D-504-5
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ITEM #: THY-303Y-C

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Long Tube Tri-Y Headers with Adapters
366-454 Big Block V8 (no smog fittings)
Part# THY-303Y-C

Technical details

1973-91 Chevrolet GMC Pickup Truck / Suburban / Full-size Blazer / Jimmy
Application notes:
 2WD ONLY | Will not fit D-port cylinder heads

1975-01 GM Class A Motorhome (P30 Chassis)
Application notes:
 1996-01 may require EGR fitting, check your vehicle and call for details if needed | Will not fit D-port cylinder heads

Header Style: 4:2:1 Long Tube Tri-Y Headers
Material: Steel
Finish: Silver Ceramic Coated
Weld Up: Yes, adapters must be welded to exhaust system
Primary Tube Diameter (in): 1-3/4"
Primary Tube Gauge: 14 Gauge
Collector Attachment: 3-Bolt Flange
Collector Diameter: 2-1/2"
Tuned: No
Flange Thickness: 3/8"
Bolts and/or Studs Included: Yes
Gaskets Included: Yes
Reducers/Adapters Included: Yes
Y-Pipe (Crossover) Included: No
Quantity: Sold as a Pair
CARB E.O. #: D-540-5 (1991-1995 MOTORHOMES 366-454 ENGINES, 1987-1991 TRUCKS 366-454 ENGINES)
Warranty: Limited Lifetime to original purchaser


Backed by over 50 years of knowledge and experience, our headers are designed to outflow your stock exhaust manifolds by leaps and bounds. Tri-Y (or 4 into 2 into 1) style headers by design will increase the power of your motor across the widest RPM band possible. That is the beauty of the design, and that is why they are the best street header available. To make these headers last, we built them using industry leading 14-gauge mild steel tubing with 3/8" thick flanges. To top all of that off, all of our headers come beautifully ceramic coated to greatly reduce under-hood temperatures and protect the headers from the environment. All 100% American made, and backed by our lifetime warranty of course!

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.


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