Exhaust System Rejuvenation

Please note: the described work was on an MGB, but the principles will apply to many vehicles.

From ‘On The Marque’ December 2021 – courtesy of G Haywood

I ordered a 12 inch long 2 inch diameter glass packed resonator to install before the rear silencer, 4 mandrel formed 45 degree bends in 2in pipe, a 2 inch diameter in and out offset 14 inch long oval free flow muffler, 4 off 2 hole steel flanges with gaskets and bolts and a metre of 2 in exhaust pipe.

I used a 120 amp wire feed welder with flux cored 0.8 mm wire to weld all joints.

Initially I used an angle grinder with a thin cut off wheel but after finding difficulty in obtaining square clean cuts resorted to using a hand hacksaw to cut the pipes.

I completely removed the old existing exhaust system and placed it on the ground. I then cut the end of the dual exhaust pipe to collector that bolts to the cast exhaust manifold and then welded an exhaust flange to the cut end.

I then placed this against the old exhaust pipe and measured the distance to fit the resonator prior to the central exhaust hanger but also to ensure the resonator would clear the chassis cross members. Then I cut the straight exhaust pipe to suit and
welded on a flange plate. Then welded the resonator to the pipe.

I measured and marked out 2 of the pre bent pipes to form a “S” bend that enabled to match the existing old exhaust pipe. When satisfied that the shape was suitable the resonator and 2 sections of bent pipe were welded together. A flange was then welded onto the end of this assembly.

Several iterations of forming another “S” bend to raise the pipe after the axle (the pipe goes under the rear axle) for the rear section were attempted before tack welding of that assembly. A flange was welded to the start of that assembly and the muffler tack welded. The final assembly was trial fitted to ensure clearance from the boot floor and end valence before final welding.

An end pipe support was fabricated to support the end of the exhaust from the rear bumper.

Finally the entire new exhaust assembly was painted with heat resistant silver paint before assembly to the car with new flange gaskets and donut gaskets to the cast exhaust manifold at the engine.