Dear Tom and Ray:
My son, 16, bought a '77 Pontiac Grand Prix. It's loud, with a big motor (muscle-car-type motor, original everything). Anyway, he sawed off the exhaust pipe to make it even louder, even though I told him he could get a ticket for this. He proceeded to tell me that this car "deserved" to be loud. Well, he got pulled over by a police officer, who told him he needed to make his car quieter. He tried to put the clamp back on it, but it doesn't hold. This brings me to my question: He asked me if duct tape will be OK to hold the pipe to the rest of the exhaust system, without starting some type of fire. I'm not a car expert, so we agreed to ask you guys.
RAY: Duct tape is pretty hearty stuff. But I don't think it's any match for pressurized, 800-degree exhaust, Rob.
TOM: Traditionally, we've always used frozen concentrated orange juice cans to patch up exhaust pipes. But sadly, they're now made out of cardboard. So we now recommend empty tomato paste cans.
RAY: Better than that, your kid can go to his local auto-parts store and buy an adapter. Almost all auto-parts stores sell metal sleeves that are either slightly larger or slightly smaller in diameter than your exhaust pipe. The sleeve serves as a coupling, where you stick the severed pieces of the exhaust pipe in either end, and then clamp them down to hold them in place.
TOM: It's a cheap repair, and it won't last forever. But based on your son's approach to this car, I don't think you're going to need to plan for forever.
RAY: If you want something a little more permanent, or if he cut it too close to the muffler for the sleeve to work, take the car to a garage or a muffler shop, and ask them to butt the pipes together and weld them.