October 1, 2018

Updated Jan 11, 2020

The first thing you need to know about the 1968 Shelby engine is Ford used the code "S" to denote the 428 Police Interceptor engines.
This caused some problems, because the Ford Mustang used the same code for a 390 engine. There were no Shelbys with 390 engines.

This bulletin was sent to dealers in 1968 explaining the confusion.

The engine code used on the GT500 4 speed transmission was "405 J04".

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 Metuchen assembly line workers to install the 4 speed version of the Ford 428 Police Interceptor. This engine would have a flywheel and clutch, pressure plate installed.

All 4 speed engines received thermactor emissions (smog). The also started with a Ford Autolite carburetor. All Shelby 428 PI, 4 speed engines were built to the same specifications. The code number would also be present on the engine tag. Factory options, like power steering and air conditioning, do not change the basic engine configuration.

The air cleaner on a GT500 is the same as the GT350. The GT500s did not use ram air.

You may be surprised to learn that all GT500s started off from Ford with the C8AF-9510-AE, Autolite carburetor.

These carburetors were supposed to be removed at AO Smith and replaced with the Holley carburetor. I have documented several cars that did not have the carburetor changed out. They all appear in the same time frame.

The Holley carburetor is much more common and carries the ID Number C8ZX-9510-A. The carb only has one application and was used on both 4 speeds and automatic transmissions. You can see the carb dashpot in this picture. It is different from the more common, Cobra Jet dashpot.

A lot of restorers get this detail wrong. The C7AE-9425-F aluminum, intake manifold was painted blue with the engine assembly at Ford.

The back of the intake manifold has a pedestal that was usually unpainted (top-center). Please note the vacuum fittings lower right. The fitting that screws into the intake manifold is painted. The secondary fitting remains unpainted brass.

Here is a picture of the vacuum fitting. I have seen two different fitting used on the 428 PI engines. This is the more common one.

This house shaped fitting, attached to the intake, was also used on some cars.

The "MX" marked vacuum hoses are more common on later cars, but some early cars did have them as well.

The GT500 shares the same valve covers with the GT500 KRs. The gaskets for these covers were originally painted silver.

I have seen several GT500s that had this small idle compensator valve in the PCV hose. This PCV remains unpainted, although they are more commonly painted blue with the engine.

The oil cap is a chrome Autolite cap with a gold dichromate fitting. The hose to the air cleaner is the same as the GT500 KR, but it is routed to the back of the oval air cleaner.

These are the 428 Police Interceptor, cast iron exhaust manifolds.

The engine lift hooks were mounted to the exterior of the exhaust manifolds. The ones I have seen were painted black. Sometimes these were removed at the factory.

I have also seen a couple of GT500s with a heat shroud. This part was unnecessary, but may have been left on the engines in error. If you have a GT500 with one of these still on the engine, please drop me an email.

All GT500 blocks have a casting date. It is located between the oil filter and the oil pan rail. Here "8A11" translates to January 11, 1968. That's Carroll Shelby's birthday! The "E1" relates to the casting plant.

ALL GT500s, regardless of transmission came from the factory with emissions pumps. Here is a picture of one on an air condtioned car.

GT500s used a C80E-B fan blade with a C8ZX-A fan clutch.

405 J04 GT500 / 4 speed

Pulley Pulley ID Number Sheaves
Crankshaft C8AE-6312-D 3
Water Pump C8OE-8509-A* 3
Alternator Steel 2
Power Steering 6AA 1
Thermactor C8AE-9C480-A 1

* No visible stamping on pulley

405 J04 GT500 / 4 speed

Pulley Pulley ID Number Sheaves
Crankshaft C8AE-6312-A 3
Water Pump C6AE-8509-A 3
Alternator Stamped Steel 1
Power Steering AF 1
Thermactor C8AE-9C480-B 1
AC Idler Fixed C8AZ-8678-B* 1
AC Idler Adjustable C8AZ-8678-A* 1

* No visible stamping on pulley