Dual Exhaust Crossover Pipe

Over a year ago I had a local muffler shop install a new dual exhaust, including Dynamax mufflers. And they did a great, clean installation.

It is claimed by many that a dual exhaust increases horsepower (or at least overall performance) by reducing backpressure.

Not sure if that's actually a correct assumption and, frankly, I did not notice any difference as far as performance was concerned.

If a dual exhaust does help performance, that is great, but a true dual exhaust can also create other less-desirable issues, as I was going to find out.

Enter Exhaust Wavelength Resonating Frequencies, and you can end up with an annoying drone as it happened in my case.



Between 1500 and 2500 RPM, there was this up and down reverberating drone that I noticed the moment I drove the car out of the muffler shop. I called the shop owner and he thought that an X-pipe would take care of the issue.

But, unfortunately, there is not enough room under a C3 Corvette to do this in a manner that will keep the pipe tucked close enough to the underside to avoid hitting speed bumps or interfering with the emergency brake, for example.

So the solution to my dilemma, I hoped, was to have a crossover or "H" pipe installed, and I had the shop do exactly that.

Danny, one of the owners, managed to add the crossover pipe with the exhaust in place, which saved me time and money.

As the photos below show, he fabbed the crossover from a piece of pipe of the same diameter and placed it right before the spare tire carrier, so it would be out of the way.

He then cut openings on each exhaust pipe with a plasma cutter and then prepped the area for welding.

The crossover pipe itself had to be reshaped a bit to prevent any exhaust fume leaks. When Danny was satisfied with the fit, he welded the crossover in place.

And this is the finished product. Out of the way of things and ready for duty.

But "did it work?" you ask.

Yes, it did.

The annoying drone is now a thing of the past, so at least for my application, this was the solution to this problem. There are, of course, countless things that can help create or aggravate a droning sound issue. Things such as exhaust pipe bends or even the type or brand of mufflers used can be a factor, so there are no guarantees that an X or crossover pipe will work for every situation.

But I was fortunate that this fix was the solution in my case.

Thanks for following my '76 Vette Blog!

Product Links... (#sponsored)

• How to Restore Your C3 Corvette: 1968-1982
• 1968-1982 Corvette Restoration Guide, 2nd Edition
• 1976 Corvette Assembly Manual

Borla Pro XS Muffler 2.5 in. Inlet/Outlet | Oval Body 19 in.