|The MGA With An Attitude
EXHAUST SYSTEM, Twin Cam - TC-118
The MGA Twin Cam exhaust system starts with a two-piece iron manifold dropping to dual flanged outlets. This is followed by dual down pipes welded to a 2-into-1 collector, followed by an intermediate pipe and muffler. Originally the intermediate pipe and muffler were welded as a singe assembly, although the intermediate pipe had an additional part number to be purchases separately as a Service Part. There are two bracing straps to attach the down pipes to the engine rear plate so the pipes will move with the engine so as not to damage the bolted flanges or sealing gaskets.
In the illustration the muffler is drawn horizontal, but when installed
the muffler is angled upward at the back end for better ground clearance.
It is important to properly install the two straps that secure the down pipe to the bellhousing bolts. One strap alone is not sufficient. If these straps come loose the pipe will wobble about due to engine vibration and shake, and the pipe to manifold seals will be damaged causing exhaust leak. It could even cause fracture of the pipe or the iron manifold. As a side note, the exhaust ring seal is the same part number as is used for the pushrod engine MGAs.
The intermediate pipe will be straight and level (parallel to the floor) and parallel to centerline of the vehicle from front end past the center hanger. As the pipe passes under the rear axle, there is a slight dip and a strong curve toward the centerline of the car, away from the leaf spring and shock absorber link, then back outboard again. Aft of the rear axle the pipe finishes with a slight upward angle but parallel to the centerline of the car as seen from top. The muffler will be positioned parallel to and half way between leaf spring and fuel tank with back end angled upward. The muffler ports should be positioned at lowest point with the center of the muffler body directly above the center of the pipe. The outlet tip should point to 2-o'clock position, inboard of the bumper overrider and just below the bumper facebar.
Intermediate pipe, upright, as viewed from left side.
Rolled 1/4 turn, (with "U" hanger toward you (as viewed from top).
Rolled 1/2 turn, inverted, upside down (still viewing from left side).
Rolled 3/4 turn (with "U" hanger away from you (as viewed from bottom).
Intermediate pipe viewed from front end slightly above the plane. First picture below left has the pipe upright with center hanger up. Successive photos have the pipe rotated clockwise in 90-degree steps.
There is some effort to post these pictures, because some aftermarket exhaust systems may not align properly as received. In particular the current Falcon stainless steel exhaust for the Twin Cam may not have the correct angle bend on the back end pipe of the 2-into-1 collector, which causes the intermediate pipe to be substantially misaligned farther back (like 9-inches offset at the middle hanger). The easier fix for this may be to bend the intermediate pipe near the front end.
On 2/22/2017, James Alcorn of Autovintagery wrote:
"The intermediate pipe on both Bell and Falcon exhaust systems must be modified, bent AND have the bracket moved for proper fitting"!