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Doug's Headers D521-B Full Length Header 1-3/4 In, 65-68 Catalina, Blk
Doug's Headers D521-B Full Length Header 1-3/4 In, 65-68 Catalina, Blk

Doug's Headers D521-B Full Length Header 1-3/4 In, 65-68 Catalina, Blk

389 Pontiac V8, 400 Pontiac V8, 421 Pontiac V8, 428 Pontiac V8, Full-length Header Tube Type

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Doug's Headers D521-B Full Length Header 1-3/4 In, 65-68 Catalina, Blk
Doug's Headers D521-B Full Length Header 1-3/4 In, 65-68 Catalina, Blk
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We estimate this item will ship on or before November 20th.
Part # 447D521B
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Important Messages:

  • This item ships directly from the manufacturer. It may take an additional 2 business days for Dougs Headers to ship this item.
  • Get FREE shipping when your order includes this item and exceeds $99! Ground shipping only in the contiguous US.
  • This item ships via Ground Shipping only. Expedited and Air shipping options are not available.


Header Tube Type:
Hi-Temp Black
Flange Style:
D Port
Primary Tube Diameter:
Material Type:
MFG. Part #:
Collector Diameter:
3 Inch
Hardware Included:
Gasket(s) Included:
Sold in Quantity:
GTIN Code:


Doug's PASSENGER CAR HEADERS Long Tube Hi-Temp Black 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.

  • 3/8" Thick machined warping
  • CNC mandrel bent tubes... accurate fit & better flow
  • Precision formed long transition collectors and long tube design... reduces backpressure and increases higher RPM horsepower
  • Heavy 16 gauge tubing...longer life
  • Tubes are pre-polished to remove scratches and the header isfinished with a Hi-Temp Black Coating


1965-1966 Pontiac Bonneville 6.4L/389 V8
1967-1968 Pontiac Bonneville 6.6L/400 V8
1965-1966 Pontiac Bonneville 6.9L/421 V8
1967-1968 Pontiac Bonneville 7L/428 V8
1965-1966 Pontiac Catalina 6.4L/389 V8
1967-1968 Pontiac Catalina 6.6L/400 V8
1965-1966 Pontiac Catalina 6.9L/421 V8
1967-1968 Pontiac Catalina 7L/428 V8
1965-1966 Pontiac Grand Prix 6.4L/389 V8
1967-1968 Pontiac Grand Prix 6.6L/400 V8
1965-1966 Pontiac Grand Prix 6.9L/421 V8
1967-1968 Pontiac Grand Prix 7L/428 V8


  • Doug's Headers D521-B 1 3/4" 4-Tube Full Length Header Pontiac Catalina 326-455 65-68 Hi-Temp Black Coating
  • Black
  • Collector: 3
  • Port: D
  • Primary: 1 3/4
  • exc. states w/Calif. emission stds
  • removal or modification of locking steering column reqd
  • factory heads w/o end bolt holes must be drilled and tapped
  • with Floor Shifter
  • with A/C
  • For Off-Road Use Only
Some parts are not legal for use in California or other states with similar laws/regulations

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Q & A

  • Maintaining your headers is an important part of any hot rod. Pat gives some tips and demonstrates how well Purple Metal Polish works for keeping your headers looking great.
  • Wouldn't it be nice to get the best of both worlds out of your headers? Speedway Motors has solved that problem with our exclusive heat resistant Armor Hot Coating. Now you can keep that great look with longer life.
  • Pat shows that exhaust can make a difference on even your daily driver. Check out this video of Pat with the Hooker Muffler installed on his '03 Suburban.
  • Our Tru-Ram Exhaust Manifolds are one of our most popular items. Tim provides more details about them and gives you a great look at them.

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