January 11, 2025
Peter Disher with help from Tim Lea


Information on the 1969 Shelby - 428 Cobra Jet Engine with Automatic Transmission
Does not include 428 Automatic Super Cobra Jet cars

The 428 Cobra Jet was introduced in April 1968. All 1969 GT500s used the Cobra Jet engines. The "428 CJ" is a high performance version of the 428.
Several different versions of the engine were used depending on the build date of the car.



The specific engine code used on the 1969 GT500 with an automatic transmission was "421 S". During the year, this code changed to "421 T". These motors have some important external differences.






You can find this code on the vehicle build sheet. Engines were pre-assembled and installed as units by the production line workers. The build sheet code would have directed the Dearborn assembly line workers to install the automatic version of the Ford 428 Cobra Jet engine. This engine would have the flexplate installed for attachment to the automatic transmission.

All 428 CJ engines received thermactor emissions (smog). This includes all cars sent to Canada. All Shelby 428 CJ, automatic engines were built to the same specifications. The code number would also be present on the factory, metal engine tag. Factory options, like power steering and air conditioning, do not change the basic engine configuration (or code).






The 1969 Shelby uses a true ram air system. The air cleaner assembly is comprised of the base and the heat duct (snorkel).
The base is similar to the Mustang 428 "R code" base. However, the air cleaner does not use the upper flapper assembly used on a Mustang. Early cars with the "421 S" coded engine used the C9ZF-9601-E air cleaner.





Later cars the with the "421 T" engine used a C9ZF-9601-F air cleaner base. The C9ZF-9601-F air cleaner has a small, brass, air valve in the base.




The air cleaner lid is painted blue on a 1969 Shelby and says " COBRA JET RAM AIR". It is possible some cars did not receive the air cleaner lid decal.
The unique seal for the air cleaner is glued to the bottom of the hood.




In this photo you can see the snorkel. This snorkel is shared with the Mustangs.




The Holley carburetor is marked C9AF-9510-N. It is not unique to the Shelbys, but is Cobra Jet specific. It was used on both the "421S" and "421T" motors. The carburetor uses a dashpot (not shown).




There are two different versions of the valve covers. Some cars used a plain, unpainted ribbed cover. Others used a "428 Cobra Jet" valve cover. This cover is often called the "snake" cover.
The chrome, oil filler cap now has a plastic fitting.




These are the Cobra Jet exhaust manifolds. There is actually a visual difference between the ones made in 1968 and later years.




Most of the 1969 Cobra Jets cars started with one large and one small lift hook. This picture is courtesy of the parts supplier Dead Nuts On. (www.deadnutson.com)




One of the ways to identify a GT500 block is by the casting date. This date is found between the oil filter and the oil pan, under the car. Here "9B19" decodes as February 19, 1969. On 1969 casting dates, the first character is usually slightly raised and has two dots under it. The "W1" is the area of the casting plant where the block was made.





The GT500 automatic, distributor is identified C80F-12127-J. The automatic version will have a single pull vacuum advance.
There are three colored vacuum lines. The original, green hose has a molded 90 degree bend.




The water pump bypass hose is actually thicker than regular heater hose. It was painted blue with the engine assembly and tower clamps.



In 1969, the Cobra Jet thermactor cars used this check valve. It is for a hose that is 5/8".




The anti-backfire canister is dated and has a part number. Most original valves have a date on the bottom side.




Two different water pump pulleys were used on Cobra Jet cars. The "420S" engines used the same C8AE-A pulley as the 1968s. The "420T" engines used a larger water pump pulley marked C8AE-C. The drive belts also change because the pulleys are different diameters.

The water pump pulley for an AC car only has two sheeves and is marked C6AE-8509-A. It is the same as a earlier Cobra Jet car.





The fan for a 1969 Cobra Jet car is marked C9ZE-E. It uses the C9ZE-B fan clutch.


















This GT500 / Auto transmission engine is under restoration at Tim Lea Restorations.



Engine assemblies have more than a handful of changes during 1969. It is possible there are other variations.

If you can make a contribution, please drop me an email.