Doug's Headers - D303Y

Doug's Headers D303Y 1 3/4" Tri-Y Header Chevrolet Truck Big Block Chevrolet 68-87 Metallic Ceramic Coating

Doug's Headers D303Y 1 3/4" Tri-Y Header Chevrolet Truck Big Block Chevrolet 68-87 Metallic Ceramic Coating

Part Number: D303Y / UPC 694342506988
  • Doug's Headers D303Y 1 3/4" Tri-Y Header Chevrolet Truck Big Block Chevrolet 68-87 Metallic Ceramic Coating

Product Info
  • 3/8" Thick machined flanges...no warping
  • CNC mandrel bent tubes... accurate fit & better flow
  • Tri-Y headers yield maximum power from off idle to 4500 RPM making them well suited for applications demanding maximum mid-range torque with maximum fuel economy
  • Heavy 16 gauge tubing...longer life
  • Tubes are pre-polished to remove scratches and the header is finished with a Metallic Ceramic Thermal Barrier Coating polished to a high luster appearance offering corrosion and heat resistance up to 1400 degrees

 

 

Applications and Footnotes

Chevrolet - Class A (chevrolet chassis)
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
75 - 91 396-502 Emissions Code 3 Y Y Y Y Y N N 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Carbureted applications only
Fits P30 chassis
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - GMC 2WD TRUCKS & SUV
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
68 - 87 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1/2, 3/4, 1 Ton / 1500, 2500, 3500 TRUCKS
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
68 - 87 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
73 - 91 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
73 - 91 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - Blazer / Jimmy, Suburban, Tahoe / Yukon
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
68 - 87 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

 

 

Applications and Footnotes

Chevrolet - Class A (chevrolet chassis)
YEARS 75 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL N
STD FLR N
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Carbureted applications only
Fits P30 chassis
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - GMC 2WD TRUCKS & SUV
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1/2, 3/4, 1 Ton / 1500, 2500, 3500 TRUCKS
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - Blazer / Jimmy, Suburban, Tahoe / Yukon
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

 

 

Key for abbreviations and acronyms
2V Two valve cylinder head
DP Dual Smog Pump (emissions device)
PSIG Pounds Per Square Inch Gauge
3V Three valve cylinder head
E.O. Executive Order
RD Round Port
4V Four valve cylinder head
EGR Exhaust Gas Recirculation (emissions device)
REC Rectangle Port
A/C Air Conditioning
FLR Floor
SAP Same As (cylinder head) Port
AUTO Automatice Transmission
MCTBC Metallic Ceramic Thermal Barrier Coating
SP Single Smog Pump (emissions device)
COL Column shift
OVL Oval Port
STD Standard Transmission
COLL Collector
P/B Power Brakes
T.P.I. Tuned Port Injection
DIA Diameter
P/S Power Steering

 

 

Highlights
  • 3/8" Thick machined flanges...no warping
  • CNC mandrel bent tubes... accurate fit & better flow
  • Tri-Y headers yield maximum power from off idle to 4500 RPM making them well suited for applications demanding maximum mid-range torque with maximum fuel economy
  • Heavy 16 gauge tubing...longer life
  • Tubes are pre-polished to remove scratches and the header is finished with a Metallic Ceramic Thermal Barrier Coating polished to a high luster appearance offering corrosion and heat resistance up to 1400 degrees

Applications and Footnotes

Chevrolet - Class A (chevrolet chassis)
YEARS 75 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL N
STD FLR N
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Carbureted applications only
Fits P30 chassis
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - GMC 2WD TRUCKS & SUV
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1/2, 3/4, 1 Ton / 1500, 2500, 3500 TRUCKS
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - Blazer / Jimmy, Suburban, Tahoe / Yukon
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Key for abbreviations and acronyms
2V Two valve cylinder head
DP Dual Smog Pump (emissions device)
PSIG Pounds Per Square Inch Gauge
3V Three valve cylinder head
E.O. Executive Order
RD Round Port
4V Four valve cylinder head
EGR Exhaust Gas Recirculation (emissions device)
REC Rectangle Port
A/C Air Conditioning
FLR Floor
SAP Same As (cylinder head) Port
AUTO Automatice Transmission
MCTBC Metallic Ceramic Thermal Barrier Coating
SP Single Smog Pump (emissions device)
COL Column shift
OVL Oval Port
STD Standard Transmission
COLL Collector
P/B Power Brakes
T.P.I. Tuned Port Injection
DIA Diameter
P/S Power Steering

Emissions Code Key

The application guide above specifies which Emissions Code applies to this part. Doug's Headers uses a voluntary product identification program whereby all mission-sensitive products can be identified by placing numbered labels in product packaging and listing corresponding numeric codes next to each part number. The corresponding numbers and explanations are as follows:

This Product has been granted a California Air Resources Board (CARB) "E.O" (Executive Order) Exemption, or is considered a Direct Replacement or Consolidated Replacement part. It is 50 State Legal when installed on the appropriate vehicle per the Manufacturer Application guide and Installation Instructions

This product is Legal for use on 1974 and older non catalyst equipped vehicles and is considered a "replacement part" per California Air Resources Board regulations, as long as ALL emissions sensitive components are retained, including A.I.R., EGR, Heat Risers etc. Failure to retain any of these components, or use on any 1975 or newer catalytic converter equipped car would render this product Illegal for Street or Off Highway Use in California, or in states that have adopted California Emissions regulations and may only be used for Closed Course Competition.

This product is Not legal for Street or Off Highway use in California or in states that have adopted California Emissions Regulations and is only intended for Closed Course Competition use, except 1965 and Older US manufactured California Certified vehicles, 1967 or older US manufactured Federally Certified vehicles, or 1967 and older Foreign manufactured vehicles which may have any aftermarket add-on or modified part installed as long as the vehicle can still meet the tailpipe emission standards for the year of the vehicle and retain any original or retrofit crankcase control (PCV) devices and NOx device required for the year of the vehicle.

Additional Information

Doug's 2/4 WD TRUCK HEADERS Tri-Y Metallic Ceramic Coated Header development and design is complex and requires a substantial amount of time and resources to do the job right! Many manufacturers are unwilling to make the commitment and instead offer compromised headers at lower prices. Doug's will not compromise performance, quality or fit to compete with inferior designs at cheap prices. Every Doug's header is tuned with the proper tube size and length to efficiently remove all the exhaust from each cylinder, reducing pumping losses resulting in a dramatic increases in horsepower and torque. Doug's headers are carefully developed on the vehicles they are intended to fit and are re-checked numerous times during the design and manufacturing process.

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Instruction Manual
Instruction Manual

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Doug's Headers - D303Y

Doug's Headers D303Y 1 3/4" Tri-Y Header Chevrolet Truck Big Block Chevrolet 68-87 Metallic Ceramic Coating

Doug's Headers D303Y 1 3/4" Tri-Y Header Chevrolet Truck Big Block Chevrolet 68-87 Metallic Ceramic Coating

Part Number: D303Y / UPC 694342506988
$909.95
$909.95

Shipping calculated at checkout.
Part Number: D303Y / UPC 694342506988
  • Free shipping on $99+ orders in lower 48 states
  • 90-day return policy
  • We’re here to help! Call us on 909-599-5955
Emissions code

Emissions Code

Continue Reading to Understand Emissions Codes
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Product Info
  • 3/8" Thick machined flanges...no warping
  • CNC mandrel bent tubes... accurate fit & better flow
  • Tri-Y headers yield maximum power from off idle to 4500 RPM making them well suited for applications demanding maximum mid-range torque with maximum fuel economy
  • Heavy 16 gauge tubing...longer life
  • Tubes are pre-polished to remove scratches and the header is finished with a Metallic Ceramic Thermal Barrier Coating polished to a high luster appearance offering corrosion and heat resistance up to 1400 degrees

 

 

Applications and Footnotes

Chevrolet - Class A (chevrolet chassis)
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
75 - 91 396-502 Emissions Code 3 Y Y Y Y Y N N 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Carbureted applications only
Fits P30 chassis
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - GMC 2WD TRUCKS & SUV
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
68 - 87 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1/2, 3/4, 1 Ton / 1500, 2500, 3500 TRUCKS
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
68 - 87 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
73 - 91 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
73 - 91 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - Blazer / Jimmy, Suburban, Tahoe / Yukon
    EMISSION       AUTO STD TUBE COLLECTOR PORT
YEARS ENGINES CODE A/C P/B P/S COL FLR COL FLR SIZE (in.) SIZE (in.) SHAPE
68 - 87 396-502 Emissions Code 3 Y Y Y Y Y Y Y 1 3/4 - 2 2 1/2 SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

 

 

Applications and Footnotes

Chevrolet - Class A (chevrolet chassis)
YEARS 75 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL N
STD FLR N
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Carbureted applications only
Fits P30 chassis
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - GMC 2WD TRUCKS & SUV
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1/2, 3/4, 1 Ton / 1500, 2500, 3500 TRUCKS
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - Blazer / Jimmy, Suburban, Tahoe / Yukon
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

 

 

Key for abbreviations and acronyms
2V Two valve cylinder head
DP Dual Smog Pump (emissions device)
PSIG Pounds Per Square Inch Gauge
3V Three valve cylinder head
E.O. Executive Order
RD Round Port
4V Four valve cylinder head
EGR Exhaust Gas Recirculation (emissions device)
REC Rectangle Port
A/C Air Conditioning
FLR Floor
SAP Same As (cylinder head) Port
AUTO Automatice Transmission
MCTBC Metallic Ceramic Thermal Barrier Coating
SP Single Smog Pump (emissions device)
COL Column shift
OVL Oval Port
STD Standard Transmission
COLL Collector
P/B Power Brakes
T.P.I. Tuned Port Injection
DIA Diameter
P/S Power Steering

 

 

Highlights
  • 3/8" Thick machined flanges...no warping
  • CNC mandrel bent tubes... accurate fit & better flow
  • Tri-Y headers yield maximum power from off idle to 4500 RPM making them well suited for applications demanding maximum mid-range torque with maximum fuel economy
  • Heavy 16 gauge tubing...longer life
  • Tubes are pre-polished to remove scratches and the header is finished with a Metallic Ceramic Thermal Barrier Coating polished to a high luster appearance offering corrosion and heat resistance up to 1400 degrees

Applications and Footnotes

Chevrolet - Class A (chevrolet chassis)
YEARS 75 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL N
STD FLR N
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Carbureted applications only
Fits P30 chassis
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - GMC 2WD TRUCKS & SUV
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1/2, 3/4, 1 Ton / 1500, 2500, 3500 TRUCKS
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - 1 Ton / 3500 Crew, Standard Cab DUALLY
YEARS 73 - 91
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Big block frame stands and motor mounts must be used to insure proper engine location and header fit.
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Chevrolet/GMC - Blazer / Jimmy, Suburban, Tahoe / Yukon
YEARS 68 - 87
ENGINES 396-502
EMISSION CODE Emissions Code 3
A/C Y
P/B Y
P/S Y
AUTO COL Y
AUTO FLR Y
STD COL Y
STD FLR Y
TUBE SIZE (in.) 1 3/4 - 2
COLLECTOR SIZE (in.) 2 1/2
PORT SHAPE SAP
Available with optional smog pump provision. Dual smog pump applications add DP to the end of header part number. Single smog pump applications add SP to end of header part number
Does not fit 4 speed applications with bell housing mounts
Non catalytic converter equipped.
Tri-Y design

Key for abbreviations and acronyms
2V Two valve cylinder head
DP Dual Smog Pump (emissions device)
PSIG Pounds Per Square Inch Gauge
3V Three valve cylinder head
E.O. Executive Order
RD Round Port
4V Four valve cylinder head
EGR Exhaust Gas Recirculation (emissions device)
REC Rectangle Port
A/C Air Conditioning
FLR Floor
SAP Same As (cylinder head) Port
AUTO Automatice Transmission
MCTBC Metallic Ceramic Thermal Barrier Coating
SP Single Smog Pump (emissions device)
COL Column shift
OVL Oval Port
STD Standard Transmission
COLL Collector
P/B Power Brakes
T.P.I. Tuned Port Injection
DIA Diameter
P/S Power Steering

Emissions Code Key

The application guide above specifies which Emissions Code applies to this part. Doug's Headers uses a voluntary product identification program whereby all mission-sensitive products can be identified by placing numbered labels in product packaging and listing corresponding numeric codes next to each part number. The corresponding numbers and explanations are as follows:

This Product has been granted a California Air Resources Board (CARB) "E.O" (Executive Order) Exemption, or is considered a Direct Replacement or Consolidated Replacement part. It is 50 State Legal when installed on the appropriate vehicle per the Manufacturer Application guide and Installation Instructions

This product is Legal for use on 1974 and older non catalyst equipped vehicles and is considered a "replacement part" per California Air Resources Board regulations, as long as ALL emissions sensitive components are retained, including A.I.R., EGR, Heat Risers etc. Failure to retain any of these components, or use on any 1975 or newer catalytic converter equipped car would render this product Illegal for Street or Off Highway Use in California, or in states that have adopted California Emissions regulations and may only be used for Closed Course Competition.

This product is Not legal for Street or Off Highway use in California or in states that have adopted California Emissions Regulations and is only intended for Closed Course Competition use, except 1965 and Older US manufactured California Certified vehicles, 1967 or older US manufactured Federally Certified vehicles, or 1967 and older Foreign manufactured vehicles which may have any aftermarket add-on or modified part installed as long as the vehicle can still meet the tailpipe emission standards for the year of the vehicle and retain any original or retrofit crankcase control (PCV) devices and NOx device required for the year of the vehicle.

Additional Information

Doug's 2/4 WD TRUCK HEADERS Tri-Y Metallic Ceramic Coated Header development and design is complex and requires a substantial amount of time and resources to do the job right! Many manufacturers are unwilling to make the commitment and instead offer compromised headers at lower prices. Doug's will not compromise performance, quality or fit to compete with inferior designs at cheap prices. Every Doug's header is tuned with the proper tube size and length to efficiently remove all the exhaust from each cylinder, reducing pumping losses resulting in a dramatic increases in horsepower and torque. Doug's headers are carefully developed on the vehicles they are intended to fit and are re-checked numerous times during the design and manufacturing process.

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