Dorman® - Cast Iron Natural Exhaust Manifold

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1978 Mercury Grand Marquis
Fits Following Model(s):
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Replaces Original (OE) Part #:D5AZ 9431-A
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Product Details

Mercury Grand Marquis 5.8L / 6.6L 1978, Cast Iron Exhaust Manifold by Dorman®. Position: Driver Side. Color: Natural. Header Coating: Uncoated. This product is made of high-quality materials to serve you for years to come. Designed using state-of-the-art technology and with customers in mind. It will meet your needs and deliver great quality at an affordable cost.


Header Material: Cast Iron
Finish: Natural
Position: Driver Side
Heat Shield Included: No
Installation Hardware Included: Yes
Package Quantity: 1
Manifold Bolt Hole Quantity: 8
Packaging Type: Box
Gasket or Seal Included: No
Flange Bolt Hole Quantity: 0
Flange Stud Hole Quantity: 2
Item Grade: Regular
Inlet Port Shape: Oval


  • High Quality tubular construction protects against warping and/or cracking
  • Leak-resistant for long-lasting performance
  • This part conforms to product standards


  • Exhaust Manifold
  • 4 Studs
  • 2 Nuts

A rigorous quality inspection has been undertaken to ensure that this part conforms to product standards. More like a complete kit than a single part, many of the Exhaust Manifolds include gaskets and hardware for a complete installation.

When you want to get OEM quality without the high dealer price, Dorman is the right choice for you. Today you can fix your vehicle properly and have money left in your pocket with a Dorman product. It will look, function, and fit just like the part from the dealer, so your vehicle will operate as it should or even better. The Dorman product is designed using state-of-the-art technologies to exactly replicate the OEM unit, then it is manufactured with modern tooling so that the end product looks and fits exactly as designed. The unit is made to the same dimensions as the OEM part with the same gauge material. Dorman is confident in the quality of their products, which is why the company covers them with a limited lifetime warranty against any defects in materials and workmanship. Easily restore the appearance and function of your vehicle with Dorman products.

Dorman Products Inc. is well-known as a leader in providing quality auto parts to the aftermarket. They have earned their reputation for excellence from over three decades of experience in providing automotive replacement parts, fasteners and service line products primarily for the automotive aftermarket. Their prestigious position stems from a unique combination of application expertise, innovative product design, and breadth of product offerings, many of which are not conveniently or economically available elsewhere.

California Residents

WARNING This product can expose you to chemicals including nickel (metallic) which is known to the State of California to cause cancer.

Part Number:
OE Numbers:
D5AZ 9431-A


  • Hybrid battery – fleet: 12 months from the date of purchase
  • Hybrid battery – non-fleet: 36 months from the date of purchase
  • Manifold Converters: 60 months or 50,000 miles from the date of purchase
  • Heavy Duty DPF / DOC: 24 months from the date of purchase
  • Light Duty DPF / DOC: 24 months or 36,000 miles from the date of purchase
  • Heavy Duty EGR Coolers: 36 months from the date of purchase
  • Light Duty EGR Coolers: Limited Lifetime
  • All other products: lifetime

Dorman Products warrants that the product is free from defects in material and workmanship under normal use and service for the period stated above. Dorman will replace any of its products that in Dorman's reasonable determination does not comply with the foregoing warranty. This warranty becomes null and void if the damage is caused by: misuse, abuse or accident; the attachment of any unauthorized accessory; alteration to the product; improper installation; exposure to harsh weather and/or chemicals; or lack of proper maintenance. This warranty also becomes null and void if the product is opened or any sticker is tampered with, broken, or missing, or if the damage is caused by any other condition that is beyond the control of Dorman Products.

In all cases, Dorman shall not be responsible for any type of incidental, consequential, or special damages. All other warranties, including the implied warranties of fitness for a particular purpose and the implied warranty of merchantability, are excluded.

By accepting this product, you hereby waive and release any claim now or hereafter existing against Dorman Products, its employees, officers, directors, agents and customers, on account of any and all claims, demands, suits, causes of action and all legal proceedings, whether civil or criminal, damages, losses, liabilities, (including, but not limited to, strict liability in tort), obligations, penalties, judgments or fines and other sanctions.

Federal and/or state laws may provide you with other warranties for this product. Some states do not allow the exclusion or limitation of incidental or consequential damages.

Magnuson-Moss Warranty Act:
Legally, a vehicle manufacturer cannot void the warranty on a vehicle due to an aftermarket part unless they can prove that the aftermarket part caused or contributed to the failure in the vehicle (per the Magnuson Moss Warranty Act (15 U.S.C. 2302(C)) Learn More

Vehicle Fitment

Ford Bronco
1981 Ford Bronco
  • 5.8L
1980 Ford Bronco
  • 5.8L
1979 Ford Bronco
1978 Ford Bronco
Ford Custom
1977 Ford Custom
1976 Ford Custom
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1975 Ford Custom
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Ford E-series
1982 Ford E-series
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1981 Ford E-series
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1981 Ford E-250 Econoline / E-250 Econoline Club Wagon / E-350 Econoline / E-350 Econoline Club Wagon
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1980 Ford E-series
  • 6.6L
1980 Ford E-150 Econoline / E-150 Econoline Club Wagon / E-250 Econoline / E-250 Econoline Club Wagon / E-350 Econoline / E-350 Econoline Club Wagon
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Ford F-100
1979 Ford F-100
  • 6.6L
1978 Ford F-100
  • 6.6L
1977 Ford F-100
  • 6.6L
Ford F-150
1981 Ford F-150
  • 5.8L
1980 Ford F-150
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1979 Ford F-150
  • 6.6L
1978 Ford F-150
  • 6.6L
1977 Ford F-150
  • 6.6L
Ford F-250
1982 Ford F-250
  • 6.6L
1981 Ford F-250
  • 5.8L / 6.6L
1980 Ford F-250
  • 5.8L / 6.6L
1979 Ford F-250
  • 5.8L / 6.6L
1978 Ford F-250
  • 5.8L / 6.6L
1977 Ford F-250
  • 5.8L / 6.6L
Ford F-350
1982 Ford F-350
  • 6.6L
1981 Ford F-350
  • 5.8L / 6.6L
1980 Ford F-350
  • 5.8L / 6.6L
1979 Ford F-350
  • 5.8L / 6.6L
1978 Ford F-350
  • 5.8L / 6.6L
1977 Ford F-350
  • 5.8L / 6.6L
Ford LTD
1979 Ford LTD II
  • 5.8L
1978 Ford LTD / LTD II
  • 5.8L / 6.6L
1977 Ford LTD / LTD II
  • 5.8L / 6.6L
1976 Ford LTD
  • 5.8L / 6.6L
1975 Ford LTD
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Ford Ranchero
1979 Ford Ranchero
  • 5.8L
1978 Ford Ranchero
  • 5.8L / 6.6L
1977 Ford Ranchero
  • 5.8L / 6.6L
1976 Ford Ranchero
  • 5.8L / 6.6L
1975 Ford Ranchero
  • 5.8L / 6.6L
Ford Thunderbird
1979 Ford Thunderbird
  • 5.8L
1978 Ford Thunderbird
  • 5.8L / 6.6L
1977 Ford Thunderbird
  • 5.8L / 6.6L
Mercury Cougar
1979 Mercury Cougar
  • 5.8L
1978 Mercury Cougar
  • 5.8L / 6.6L
1977 Mercury Cougar
  • 5.8L / 6.6L
1976 Mercury Cougar
  • 5.8L / 6.6L
1975 Mercury Cougar
  • 5.8L / 6.6L
Mercury Grand Marquis
1978 Mercury Grand Marquis
  • 5.8L / 6.6L
1977 Mercury Grand Marquis
  • 6.6L
1976 Mercury Grand Marquis
  • 6.6L
1975 Mercury Grand Marquis
  • 6.6L
Mercury Marquis
1978 Mercury Marquis
  • 5.8L / 6.6L
1977 Mercury Marquis
  • 6.6L
1976 Mercury Marquis
  • 6.6L
1975 Mercury Marquis
  • 6.6L
Mercury Montego
1976 Mercury Montego
  • 5.8L / 6.6L
1975 Mercury Montego
  • 5.8L / 6.6L
Low Prices Price match guarantee
Guaranteed Fitment Always the correct part
In-House Experts We know our products
Easy Returns Quick & Hassle Free

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