In the movie American Graffiti, John Milner (Paul Le Mat) gets wind of Bob Falfa’s (Harrison Ford) desire to take on the reigning street king. So prior to meeting up with the ’55 Chevy, Milner took his ’32 Ford to a local garage and crawled under it to uncap his headers for the upcoming race.
That’s how hot rodders used to find a little extra power from their street machines back in the early years of street racing, it was as close as they could get to running open headers without unbolting the exhaust system. Passenger car mufflers can be a bit restrictive when other modifications have been done, such as a bigger carburetor and headers.
Installing a cutout pipe (Y-pipe) after the header collector with a block-off plate was the easy solution to finding a little more power in a choked off engine. To “uncork” the headers, as they called it, removing the block-off plate was easy to do, albeit a bit cumbersome because it required laying on the ground or putting the car up in the air. It took longer to access the cutouts than it did to remove the plate.
Today, the block-off plate can be eliminated by installing a Jegs Electric Exhaust Cutout Kit (Jegs part #555-30831K). Josh Quellhorst at Jegs says, “For the dragstrip where open exhaust is allowed, it quickly allows easy access with the push of a button for a little extra performance.” But he’s also quick to add that one other trait that enthusiasts love even more about cutouts is the sound they get when they’re opened up at a car show or cruise.
For those who want a little more rumble from their musclecar, this affordable kit provides the ability to open up the headers for the deepest rumble, or close them up to keep the neighbors happy. An included rocker switch is all it takes and you can go from mild to wild in just a matter of seconds.
Opening the cutouts will increase the decibel level coming from the exhaust because it is essentially running an open header. A majority of the exhaust fumes and noise will exit at the cutout, so it is also imperative that they are angled away from the center of the car, preferably towards the rocker panel.
Cutouts have the potential to provide some vehicles with more power, but it ultimately depends on the engine build. This is not a guarantee with all vehicles. A built engine with a performance exhaust might not benefit as much as a car with restrictive, passenger mufflers. It basically depends on how much back pressure the exhaust has to begin with; three-inch cutouts on a stock engine might not provide an increase in anything but sound level. But that’s the cool part of cutouts for a street car, anyway.
The engine is a big air pump and in order for it to make power it needs to have some form of back pressure. Try blowing through a tube (from a roll of paper towels), then try blowing through a straw and you’ll see what we mean by back pressure. The straw will restrict the flow of air and the air that exits the opposite end of the straw will have a little more force. It’s much easier to blow through the tube than it is through the straw, but you can put a little more force behind it with the straw.
Making Some Noise
Cutouts are a favorite for weekend warrior type drag racers because they allow the driver to maintain reasonable sound levels on the way to the track. Once at the track, the cutouts are opened up and the potential for a couple extra ponies is literally at their fingertips.
We installed a set of cutouts on this daily driven car because the owner wanted to show off a little at cruise nights and car shows. Wowing the crowd with his cutouts was the main goal here and it’s a common install. Some car shows have an “open header” competition where the crowd reaction determines the winner, and that competition always draws a big crowd. What enthusiast doesn’t like the sound of open headers?
With our subject vehicle up in the air on our BendPak lift, the first part of installing cutouts required finding a suitable location for the Y-pipe with room to mount the electric motors. The motors on the Jegs kit are compact, making them easier to install. The motors have a stainless steel shaft and butterfly, and the cases are sealed to keep dirt, grease, and moisture from contaminating the electric components.
The motors should be installed where they are a bit protected and not hanging down low where they might come in contact with debris on the road or speed bumps. Most of the time they’re installed as close to the header collector as possible, but they can be installed further down the exhaust if space is an issue.
The Y-pipe kit included with our electric cutout kit can be purchased separately in 2.5-inch (Jegs part#555-30751) or 3-inch (Jegs part#555-30752) kits to match common exhaust sizes. The pipe was installed in line with the exhaust with the exit facing outwards. The Y-pipe should be parallel to the ground if possible and not pointed downwards. We added a short turn-down on our Y-pipes to force the air downward, a simple task for our Miller Millermatic 252 digital mig welder.
The electric motors have a plug for the harness, and the harness was run through a body plug on either side of the vehicle and up through the interior to the location where we mounted the switch. The switch can be mounted anywhere in the interior, with a recommendation to mount it where it can be accessed but out of the way so that it can’t be accidentally activated.
The car owner chose a spot inside the center console where it was down low and somewhat hidden, but easy to get to. For many, the switch might not be activated frequently (at least once the initial cool factor wears off from opening them at every stop light) so mounting the switch on the dash isn’t necessary. A switched 12 volts (ignition-on) and a solid ground is all that is needed to activate the electric motors, and the install was completed in less than four hours.
The kits do require some welding, so having them installed at an exhaust shop or by an experienced welder is paramount to avoid exhaust leaks under the car (when the system is closed). The results? Ear to ear grins from both car owner and his gearhead teenager who begs dad to open them up so she can hear that rumble.
The cutout kits are available from the Jegs website in both 2.5-inch and 3-inch sizes, both with and without the electric motors. Jegs also has plenty of other performance parts and accessories under their own label, as well as thousands of other name brand parts in their bi-monthly catalog, which you can receive free for the asking.