The 1968 SHELBY SMOG PAGE
How can I tell if my car came equipped with emission controls?
Emission control, also called Thermactor or "smog" is actually quite common on 1968 Shelbys.
You certainly would not know that by looking at cars today. Many systems were removed in the '60s.
Owners quickly recognized the system was not a performance enhancement.
Here are some things you that may help you in determining if a car originally had the pollution control system...
What state was the car originally shipped to? Some states, like California, required pollution controls.
Is the car equipped with ports in the heads for the emissions system?
Does the car have any emission brackets?
What type of pulleys are on the car?
If you have a question regarding whether or not a specific car should have smog. I recommend you contact the Shelby American Automobile
Club. They have production records and warranty service records on almost all 1968 Shelbys.
The GT 500 KR
Most knowledgable people agree all 428 Cobra Jet cars, regardless of transmission,
had the smog systems installed when they left the factory. Shelby did not modify the motors by removing smog components.
All GT 500 KRs are Cobra Jet cars, therefore they all originally had the smog components.
This is the water pump pulley for a big block car. It has three sheaves. Cars with AC used the two sheaved pulley on the right.
The drive belts are also routed differently.
The pump bracket is used for adjustment of the belt.
Two check valves are used. The check valve is part number C8AZ-9A487-A.
This bracket holds the alternator and the smog pump on a big block. It is mounted to the water pump.
Most smog cars still have this bracket in place, even if the smog has been removed.
The GT 500
I can tell you at least some GT 500s did come with pollution control. I have seen several GT 500s with the original systems intact.
I have inspected at least three original automatic transmission cars and three original 4spd cars with the Thermactor. The GT 500 system is the same one used on the GT 500 KRs.
The smog pump is the same for small and big blocks cars. Although the pulleys change with application.
The anti backfire cannister is the same for both small and big block cars.
The GT 350
If your GT 350 was originally equipped with a 4 speed transmission, it came with pollution controls. At least some automatic cars also had the systems.
I have seen some indication that two different systems, may have been used. In concours judging the Thermactor is required for all 1968 GT350 4spds.
The check valves are the same part used on the big block Thermactor systems. They differ from pre-1968 valves.
These are the brackets for the GT 350. The blue one is for the anti backfire cannister. It is ID number C80E-9C486-A.
Compare the pump adjustment bracket to the one above.
The GT 350 pump bracket is made of cast iron.
This picture shows an original NOS 1968 302 smog tube. Both sides use the same tube. The tube is similar to some of the early style small block tubes. In 1968, the check valve fitting is 2 1/2
inches from the end of the tube. On pre-1968 cars it is closer to the end of the tube.
I know there is a lot of bad information about smog. There are many reasons people refuse to admit their car was
originally equipped with smog. The parts can be difficult to locate and are expensive. If you do the math, more than half of the 1968 Shelbys originally had smog systems installed.
The case for smog- Part 2
I got to thinking and maybe this will help. Engine assemblies were built on a seperate production line and sent to
to the assembly plant to be mated with cars.
I found this picture in an old Mustang magazine. It shows the engine assembly area. Each engine is built to the same specifications
for its specific application. Here are 428 Cobra Jet motors. The decal on this engine shows "407J". That is for an automatic transmission.
(This picture shows 1969 motors)
If we know all "407J" engines were the same, we should be able to tell which 1968 Shelbys had smog by looking at the engine codes on
Here is the code on the bottom of a build sheet. 1968 Shelbys used six codes, regardless
of their shipping destinations.
According to build sheets these codes were used on 1968 Shelbys:
283 JO1 302/4spd/Thermactor
284 JO1 302/Auto/IMCO
405 JO5 428PI/Auto/Thermactor
405 JO4 428PI/4spd/Thermactor
If you have any insights, I would like to hear from you.