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Project 1972 MGB GT Gets a New Magnaflow Exhaust

And, exhale

Ezekiel Wheeler
Mar 8, 2016

Internal combustion engines make glorious noises; some better than others. For the most part, your fantasy of ripping off a muffler and letting your mechanical beast snap, crackle, and pop its way into your heart and your neighbors' eardrums isn't entirely practical. As the saying goes, everything in moderation.

When the 1972 MGB GT arrived, the exhaust system was literally hanging on by a few spot welds and questionable hardware. It's surprising that after racking up nearly 500 miles, the thing didn't fall off. This needed rectifying; besides, the car sounded like it was gargling a giant pile of mushy peas. I put a call in to the gurus at Magnaflow Exhaust to help fix my flatulence.

1972 mgb gt factory exhaust Photo 2/19   |   The factory exhaust was held on with tack welds and hope.

The production line at Magnaflow isn't exactly cranking out units to fulfill the huge demand for '72 MGB GTs. Which means the red carpet treatment had to be rolled out for this little beauty. Don't go thinking you need our connection for a system like this. Just about any well-qualified, local Magnaflow dealer should be able to handle this. The main reason for turning up to get the VIP treatment from the team was to identify all of my options and to see the variety of solutions they offer.

1972 mgb gt magnaflow exhaust install magnaflow facility Photo 3/19   |   1972 Mgb Gt Magnaflow Exhaust Install Magnaflow Facility
1972 mgb gt magnaflow taillight Photo 4/19   |   1972 Mgb Gt Magnaflow Taillight

Some do-it-yourself builders might overlook everyday functionality for symphonic pleasure. A well-sorted build quickly goes south after you hear, "PUT A STRAIGHT PIPE ON IT!" This is all too common amongst basement-dwelling YouTube keyboard engineers no matter the subject. Mom's minivan? Straight pipe it. Grandpa's Cadillac? Straight pipe it. That $1 million super car, which received countless hours of engineering…you get the picture.

Magnaflow has a different approach. Yes, the "straight pipe everything" mantra is entertaining and could be a bit more cost effective, but you ultimately have to live with the noise until your friends convince you you're an idiot for having done it. Of course, if it takes them more than a week, you won't be able to hear their jibes anyway.

We spent time with Richard Waitas, senior manager and spokesman for Magnaflow. He helped select piping diameter, a muffler, and to map a path of success for our MGB GT—the results of which were astounding! More on that later.

1972 mgb gt magnaflow exhaust install exhaust mapping Photo 5/19   |   1972 Mgb Gt Magnaflow Exhaust Install Exhaust Mapping

First, the MGB GT had a very unique flanged header collector outlet. As you might imagine, Magnaflow didn't have this bit on its shelves. We had no choice but to salvage this strange little nub off the factory exhaust in order to ensure a proper fit to the manifold.

1972 mgb gt magnaflow exhaust install factory exhaust flanges Photo 6/19   |   The two flanges shown had to be reused to mate up the factory exhaust manifolds.

Next up was mapping out a path for our exhaust and selecting components that would allow the greatest efficiency. The first component, the round can muffler, the crew obviously had on hand. The second, and more difficult component had to be built—a beautifully welded 2-to-1 Y-Pipe that allowed both 1.75-inch downpipes to merge into a single 2-inch pipe.

1972 mgb gt magnaflow exhaust install muffler Photo 7/19   |   Compact and light yet still effective at attenuation.
1972 mgb gt magnaflow exhaust install muffler Photo 8/19   |   1972 Mgb Gt Magnaflow Exhaust Install Muffler
1972 mgb gt magnaflow exhaust install muffler Photo 9/19   |   1972 Mgb Gt Magnaflow Exhaust Install Muffler
1972 mgb gt magnaflow exhaust install custom y pipe fabrication Photo 10/19   |   The custom Y-pipe being fabbed up off the car.

This set the tone for a "high-and-tight" blueprint for the remainder of the system. The fabricator and I decided to look into the future for any other muffler needs, repairs, or maintenance. We decided to break up the system into three sections with a single outlet.

1972 mgb gt magnaflow exhaust install piping Photo 14/19   |   1972 Mgb Gt Magnaflow Exhaust Install Piping

"The 2-inch tube system is perfect for creating the right amount of back for the 100-120hp engine," Richard told us as my modern car mind was thinking that 2.5-inch pipes were the way to go. "Selecting a larger pipe is great if you have the power to back it up. Balance is the key to efficient performance and a great sound. Know your setup, plan for the future, and you can't go wrong."

1972 mgb gt magnaflow exhaust install exhaust pipe pieces Photo 15/19   |   1972 Mgb Gt Magnaflow Exhaust Install Exhaust Pipe Pieces

A few hours into the teardown, we had a plan and the proper parts. The best thing about watching your custom system come together is a skilled welder showing you what years of training begets. It looks so easy, you think about picking up your own MIG welder at Home Depot. It isn't that easy—believe me.

1972 mgb gt magnaflow exhaust install welding Photo 16/19   |   1972 Mgb Gt Magnaflow Exhaust Install Welding

The pieces of the system were finalized, tested for leaks, and bolted up. The 2-inch slash cut tip was the perfect touch. It's a bit stealthy and has vintage appeal. We weren't going for the flash of modern, disproportionate tips popular these days. Vintage cars do benefit a touch of class from time to time.

1972 mgb gt magnaflow exhaust install slash cut tip Photo 17/19   |   Slash-cut tip is vintage-sexy.

As the fabricator jumped into the driver seat, I began to give him the rundown of how to fire up the car. "Pull the choke out, pump the gas a few times, and then depress the clutch. If that doesn't work, then repeat a few more times." He looked at me, plunged the key in, pressed the clutch, and as fate would have it, the sucker fired right up as if it were a new car right off the showroom floor.

1972 mgb gt magnaflow exhaust install exhaust Photo 18/19   |   1972 Mgb Gt Magnaflow Exhaust Install Exhaust

The sound is brilliant; I could actually hear that APT cam puttering away while the ring and ping of free-flowing exhaust brought smiles to the entire shop. Work nearly stopped for a moment as anyone within earshot came over to say how much they enjoyed having something unique to mock up and hear it come to life—surprising in a shop that often sees cars with starter motors more powerful than my car. This just reinforces how the entire team at Magnaflow is made up of actual car fanatics.

1972 mgb gt magnaflow exhaust install exhaust mounting Photo 19/19   |   1972 Mgb Gt Magnaflow Exhaust Install Exhaust Mounting
By Ezekiel Wheeler
270 Articles

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