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

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

389 Pontiac V8, 400 Pontiac V8, 421 Pontiac V8, 428 Pontiac V8

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Doug's Headers D521 Full Length Header, 1-3/4 In, 65-68 Catalina, CC
Doug's Headers D521 Full Length Header, 1-3/4 In, 65-68 Catalina, CC
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We estimate this item will ship on or before May 25th.
Part # 447D521
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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.


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Doug's PASSENGER CAR HEADERS Long Tube Metallic Ceramic CoatedHeader 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 flanges... no 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 Metallic Ceramic Thermal Barrier Coating polished to a high luster appearance offering corrosion and heat resistance up to 1400 degrees

Installation Instructions (PDF)


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 1 3/4" 4-Tube Full Length Header Pontiac Catalina 326-455 65-68 Metallic Ceramic Coating
  • Ceramic Coated
  • 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 and should be drilled and tapped for proper sealing.
  • 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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