Factory Five Racing '33 Hot Rod, Assembly Manual

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oxygen sensor signals are not used by the computer, because the computer has a built in program to run
the engine rich at wide open throttle. Oxygen sensors will usually be most effective when placed near the
collection point of headers because the exhaust will remain very hot, and an average measurement of all
of the cylinders can be taken. All oxygen sensors are recommended to be used when placing a fuel
injected motor into a Factory Five kit, however in the 1996-2004 models with 4 oxygen sensors, it is
suggested to purchase a by pass kit to eliminate two of the sensors. This can also be done with
modifications to the wiring harness.
Exhaust headers
1986 to 1993 Mustang headers have 1.5” tubes, and remained the same shape. 1994 to 1995 Mustang
headers still have 1.5” headers, but the collector flanges have a larger ball and socket joint. 1996 to 2004
Mustangs used cast exhaust manifolds. SOHC engines had circular exhaust ports, and the DOHC had oval
ports; however the collector flange changed in 2003 and 2004. For those installing 351 Windsor engines
there are a few companies including Ford Motorsport that carry exhaust headers for the installation of a
351 Windsor into a 1986-1993 Mustang which should be used.