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MG MGB GT V8 Factory Originals Technical - Twin Exhaust

Hi Folks. Merry Christmas.
I am looking to fit a twin exhaust on my 1975 mgb roadster V8.
I have been told I will have to buy a modified fuel tank as the drivers side pipe does not have enough room.
Is this true, and if so does any one know other options that do not mean tank modifying or repositioning?
David Tetlow
D M Tetlow

YES!!!! NO!!!!
Bob G

You can have dual exaust without moving the tank by crossing 1 side towards the rear of the transmission then running along side the other pipe. You may want to contact Glenn Towery for the details. I have seen one car he did this way & it looked nice.

Moving the tank is not that hard, & having a pipe on each side may be visually desirable. You will have to remove & replace a small section of trunk floor & reposition the fuel line & brake line, but they can be hand bent to clear.



I moved the gas tank on my 74 1/2 MGB Roadster. It only took a couple of hours. It was a simple matter of figuring out where to drill the new holes, dropping the tank, and drilling the holes, (Easier to do if itís almost empty). I used rubber grommets to fill in the old drilled holes. Where the filler part of the tank comes into the trunk, this was cut and flipped around and welded back in, a little body filler while I was repainting the trunk and it looks like stock. The hardest part was to find a combination of hose's that allowed me to route from the gas tank filler pipe to the existing hole for the gas tank filler hose in the rear panel.
With the exhaust system itself I used a cross over pipe and had some exhaust dumps welded in as well. The muffles are under the drivers and passengers seats, pretty well where the single 4 cylinder muffler was.
I ran the car with this set up for 3 years (with a heat shield to protect the wires and gas lines) until I finally had time to re-do all the electrical, gas and brake lines.
The following site has some good pictures on exhaust systems (It was slow to load for me)

Bruce Mills

I to moved the fuel tank over and it was not hard at all. I had a new filler tube made up to line up with the gas filler hole. I have 2 flowmaster mufflers one under the driver seat where the 4cyl muffler was and the other under the passenger seat floor. I had to reroute the brake and fuel lines around the exhaust but it was nothing that cant be done in a home shop. Having a pipe on each side makes the car look very nice and the flowmaster mufflers give it a great sound.
David Fuller

I built my own exhaust manifold, four in two in one, and exhaust system, two red bullet "silencers" (black now), two left side exit. A little bit noise level, but great burble.

Where are you getting it from ? or are you making it yourself ?
Nick Ashmore

I built the exhaust manifold and system and the remainder too.

David, I didn't move the tank and found I had sufficient room (about 7" I think) between the tank side and the spring on the LHS of the car for two 2.5" pipes side by side to pass through and exit side by side in the stock position. It looks fine and is not too hard to do. My car is an MGC - which is identical to an MGB once you pass the torsion bar support box under the floor. I used two mufflers - one each side longitudinally under each seat and made a right angle turn from the right one across the driveline under the nose of the diff and then another to come in line with the first pipe and then a parallel twin section to the rear body work. There is no significant warmth transferred to the tank I can detect when the car is stationary and probably even less when moving. The somewhat uneven pipe lengths are probably insignificant on a road car application but I did put an exhaust crossover before the mufflers which seems to improve noise and smoothness. Haven't had any issues with grounding or pipework colliding with moving parts. Another option? Bob Elwin
Bob Elwin

This thread was discussed between 25/12/2004 and 30/12/2004

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