The exhaust system is one of the more primary performance tools available to the enthusiast. Because performance enthusiasts aren’t looking for single exhaust systems, I 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 1963–1964 Fairlane was fitted with a single exhaust system.
This Tech Tip is From the Full Book, HIGH-PERFORMANCE FORD ENGINE PARTS INTERCHANGE. For a comprehensive guide on this entire subject you can visit this link:
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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 castiron factory header as found on the 390/406/427-ci High Performance bigblocks. The 289 High Performance exhaust manifold isn’t much different than the 351W manifold used 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.
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 1966–1974, Thermactorequipped 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.
When it comes to performance, there are many theories about how mufflers affect this dynamic. Today, exhaust system technology is such that one doesn’t have to struggle with high noise levels to achieve performance. Of all the exhaust system manufacturers, Flowmaster offers the best technology for the money. Good street performance comes from a pair of Flowmaster 3-chamber mufflers with 21⁄2- to 3-inch pipes. Large pipes don’t improve performance on the street because they move the torque curve up. Pipes in the 21⁄2- to 3-inch range keep low-end torque where it belongs.
If a stock appearance is what you are seeking, many of the vintage Ford parts vendors market factory-original whole exhaust systems, some available in stainless steel for longevity. Walker’s Dynomax exhaust systems offer an original appearance with improved flow. The choice is yours.
Written by George Reid and Republished with Permission of CarTech Inc
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