Because performance enthusiasts aren’t looking for single exhaust systems, we will examine
factory and aftermarket dual exhaust systems beginning at the manifolds.
Dual exhaust systems didn’t come into play for small-block Fords until the Mustang was
introduced in April of 1964. Contrary to popular assumption, Fairlanes, Falcons and Comets
equipped with the 221/260/289 engines were not factory equipped with a dual exhaust system.
Even the 289 High Performance engine in the 1963-64 Fairlane was fitted with a single
exhaust system.
There are very few different exhaust manifold types for small-block Fords, especially in the
performance arena. The 289 High Performance exhaust manifold offers improved breathing
over 2V and 4V manifolds, but it is not a true cast iron factory header as found on the
390/406/427ci High Performance big-blocks. The 289 High Performance exhaust manifold isn’t
much different than the 351W manifold to come later in 1969. Both types offer longer runners,
which is less restrictive than 2V and 4V types.
The Boss 302 exhaust manifold isn’t much different than a 351C exhaust manifold. Limited
clearance in a Mustang/Cougar didn’t permit the installation of a factory cast iron header on
the Boss 302. The aftermarket offers limited options for the Boss 302 enthusiast. Only long-
tube headers are available from manufacturers who offer headers for this engine. The same
tends to be true for 351C/351M/400M engines as well.
throughout the life of these castings, the basics did not. Unless you're concerned about
date-coded originality, these manifolds went unchanged from 1962 through the early 1970s.
This is a 1966 vintage exhaust manifold, C6OE-9430-D, with a casting date code of "6A27".
Beginning in 1966, Ford began fitting California-bound vehicles with an air injection system
called Thermactor. Thermactor is an exhaust emissions control system which includes an air
pump, hoses and air manifolds tied to Thermactor-specific cylinder heads. The air pump
injects air into the exhaust ports to aid in further combustion of unburned hydrocarbon
emissions. Thermactor doesn’t rob power, as most perceive it does, because the air pump
doesn’t place any significant drag on the engine. From 1966-74, Thermactor-equipped Ford
small-blocks utilized an air manifold on each cylinder bank. Beginning in 1975, Thermactor
became an internal part of each cylinder head, with ports at each end of the head for one
common manifold located at the back of the engine.
manifold is obviously different and
offers improved breathing. Here, we
compare them with standard 289
manifolds (B and D) These manifolds
are C3OE-9431-B (Left Side/Arrow C)
and C4ZE-9430-A (Right Side/Arrow A)
from 1963-66. For 1967, they are
C7ZE-9431-A (Left Side) and
C7ZE-9430-A (Right Side). The 289
High Performance exhaust manifolds
are available as reproductions from
Ford parts vendors.
High Performance pieces just mentioned. It offers
improved breathing over the 289/302-2V and 4V
manifolds without excessive header heat and
clearance problems. As you can see, 351W
manifolds vary from left to right. There is a
right-hand 351W exhaust manifold similar to the
manifold on the left.
variety of header manufacturers,
provide improved breathing with
the benefit of being a bolt-on
replacement. These are a good
alternative to long-tube headers.
Equal-length shorty headers offer
improved breathing, but difficulty
accessing spark plugs.