1968 Chevy Nova Exhaust System - Exhaustive Research

A Pair Of QTP Exhaust Cutouts Give This Bracket Nova 11 More Horsepower In Just Seconds At The Flick Of A Switch.

Frank H. Cicerale Jun 1, 2009 0 Comment(s)

Here you can see where the driveshaft flopped around and beat up the exhaust pipe. In spots, the pipe was also starting to rot through. Both the bent pipe and the rotted spots made for some area of impeded flow. It was time for some new pieces for sure.

Here you can see how the driveshaft-induced destruction went all the way up to the header flange, which broke right between the numbers one and three exhaust ports. The broken flange led to a major exhaust leak, resulting in some noticeable backfires on deceleration. The backfire was caused by cold air making its way into the hot engine. Prolonging this problem could have led to burning the exhaust valve.

With the exhaust system all beat up and, in some spots rotted through, there was no way we were going to bolt up our nice new headers to that junk. To solve that problem, we dialed up Summit Racing, which sent out one of its header-back dual exhaust systems. With the car already being equipped with a 3-inch system, we specified the same diameter pipe for our new exhaust kit. The difference between the two came in the fact that the old system was crimped, while the new system is mandrel-bent, meaning a freer-flowing system and more power. The kit came without mufflers, but that was fine with us, as the Borla XR1 race mufflers that were already on the car would be reinstalled with the new system.

While all of this new pipe was great, we asked ourselves the great question--that being, would the car make more power without the mufflers or not. The problem is, to keep the Nova legal for the class it would compete in, we needed to keep mufflers on the car with tailpipes. For those rare occasions when the car would run outside of the Street category, we wanted the option to crack her wide open and make some noise. With that in mind, we gave Barry Adler a call at Quick Time Performance (QTP). Adler listened to our situation, and promptly kicked over a set of QTP's electric exhaust cutout kits. While QTP makes the traditional-style cutouts that require you to get underneath the car and uncork the exhaust, we had to agree with Adler when he said we live in the 21st century. Hence the inclusion of QTP's 3-inch electric cutouts, which operate with the simple press of the included toggle switch.

"With these cutouts, you don't burn your hands or have to get underneath the car," Adler explains. "The cutouts come in 2 1/4-, 2 1/2-, 3-, 3 1/2-, and 4-inch sizes. We also have 2 1/4 to-3-inch diameter oval-shaped cutouts for cars that are lowered or have ground clearance problems."

Before we rolled the Nova into the installation bay for the parts install and subsequent dyno testing, we quizzed Barry on the advantages of running the cutouts, along with the ideal location. "The gains are seen everywhere," he comments. "With the ultimate exhaust system, gains of three to five horsepower are seen. With other systems that are not as free flowing, you will see more. It all depends on how restrictive the system is. The gains are seen because you are reducing exhaust restrictions. A muffler not only lowers sound, but also creates backpressure and slows down exhaust velocity. Open headers have very little to no restriction, but it also has no velocity or backpressure. Backpressure creates velocity, which helps pull the exhaust fumes out, but you don't want too much of it either."

When it came to mounting the cutouts, not only was performance a concern, but clearance was as well. "Ideally, you want the cutouts to be mounted 12 to 18 inches off of the header collector, as that is the general rule of thumb," Adler explains. "The old school method is to paint or draw a chalk line along the length of the exhaust pipe. Take the car for a couple of rips, and then check the line. At the point where the line reappears, this is where you want to put the cutout, as this is the best place in terms of flow. Of course, clearance is an issue, so keep that in mind."

In a sense, this install was a three-part deal, as we had Gil Davis of Davis Race Engines install the headers (and the killer looking Dart valve covers). Crazy Horse Racing then installed the new exhaust pipes a few weeks later, followed by W&W Auto & Truck Repair taking the time to install and wire up the QTP cutouts. The headers were easy to install when compared to the Super Comps, and the new exhaust fit perfectly, even though the mufflers, which were previously located four inches behind the headers, were moved rearward to the stock location.