After a broken driveshaft...
After a broken driveshaft mangled the exhaust system on our '68 Nova, we decided to tune it up with some new components and one small addition, that being a set of electric exhaust cutouts from Quick Time Performance.
It's a simple proposition. In the case of an engine, what the induction system sucks in, both air and fuel-wise to make power, it must pump out efficiently to make admirable power. If any exhaust gasses remain in the combustion chamber, then less fresh air and fuel is allowed in to burn. Furthermore, if the engine has to struggle to push the spent fumes through the attending exhaust system, then the powerplant will be robbed of ponies as well simply because the engine can't exhale. Think of it like this. Take a coffee stirrer and try and blow air through it. Then do the same thing with a normal soft drink straw. The soft drink straw is easier to blow through, right? That is what an engine has to deal with when equipped with a restrictive exhaust system, as it has to work harder and expend more effort to push the exhaust fumes through said piping.
With that in mind, we set out to improve the exhaust side of this '68 Chevy Nova. While the car isn't equipped with a logjam for an exhaust system, this X-body had a few problems of its own. Originally supposed to be a street/strip car, the little Chevy has spent the last nine years seeing strip duty only in the NHRA's Pro and Street categories.
Thanks to a 406ci small-block topped with Dart Pro 1 heads, a decent camshaft, an Edelbrock intake, and a worked-over Holley 750 cfm carburetor, the Nova has the capability to foray into the low 11-second zone. Thanks to the 11.50-second elapsed time limit for the Street category, ballast and a few other tricks slow the car down to consistent 11.50 runs.
To replace the broken-down...
To replace the broken-down Hooker 1 3/4-inch Super Comp headers, we went back to Hooker, though this time we ordered up a set of 1 5/8-inch Competition headers of the ceramic-coated flavor.
With consistency of the utmost concern, new attention was focused on the exhaust system, which had taken a beating thanks to a broken driveshaft at 5,600 rpm. The ensuing whipping of the 'shaft mangled the exhaust piping, and even broke the flange on the driver-side header right between the numbers one and three cylinders. With the broken flange leading to an serious exhaust leak that would result in a backfire after letting off of the throttle at high rpm, we knew that not only were we taking a chance in burning a valve with the exhaust leak, but the mangled system and said leak were costing power.
To solve our dilemma, we called up a host of suppliers to get our little Nova back to the track in better-than-before condition. We started by ditching the broken headers for a new pair supplied by Hooker. While we made a change from what was on the car, we felt the change would not only help low-end power, but installation as well. Off came the Hooker 1 3/4-inch Super Comp headers, and on went a pair of 1 5/8-inch Competition headers.
"When going from bigger to smaller primary tubes, you will have better torque," says Matt Held, formerly of Holley Performance Group. "If the size of the tube is totally wrong, you will see not only a gain in torque, but in power as well. You will also notice better throttle response."
"The Competition headers are the affordable version from Hooker. The primary tubes are equal in length, and they use 16-gauge material, making them a bit heavier. Super Comp headers will have a different primary tube size and length, and the collector is specifically tailored to the engine's horsepower output and racing needs."
The headers we chose were, which costs a bit more, but add longevity to the headers. "Ceramic coating will help control the amount of heat that radiates from the tube, thus lowering under hood temperatures," Held explains. "The ceramic actually bonds to the metal, and will protect the metal from corrosion and rust. In some harsh environments where the headers might be subjected to road salt or acid rain, the ceramic will only slow the process of corrosion."
 The cutouts are powered by...  The cutouts are powered by an electric solenoid, which gets power from a key-on power source. Flip the switch one way and the blades open, allowing the exhaust to exit before the muffler. Press it again and the blades close, giving you a full muffled exhaust. |  We figured since we were going...  We figured since we were going to be under the hood installing the headers, we might as well get rid of those leaking valve covers. Since the 406 is topped with Dart Pro 1 heads, it was only natural that we threw on a set of Dart valve covers complete with a set of Fel-Pro gaskets. Of note--we had to drill holes in the valve covers for the breather and fill cap, as the covers didn't come with that provision. |  The cutouts are powered by...  The cutouts are powered by an electric solenoid, which gets power from a key-on power source. Flip the switch one way and the blades open, allowing the exhaust to exit before the muffler. Press it again and the blades close, giving you a full muffled exhaust. |