Perhaps the concept of trickle-down economics isn’t all that far-fetched. Case in point: your author (or more correctly, his old man) recently picked up this virtually flawless, 52,000-mile C5 Z06 for just $19,000 – a full thirty grand less than it went for new. Yes, the world-class supercar we know as the Z06 has finally dropped into the econocar price bracket, and should the Corvette divinities see fit for the C6 versions to one day near this level of affordability, it will surely be the best of all possible worlds.
01. Let’s start with Callaway’s so-called Double-D Exhaust System, easily the most highly polished cat-back I’ve ever installed. Constructed of T304 stainless steel, Callaway says its design promotes maximum flow and the highest possible horsepower, along with a deep, powerful tone that’s “excitingly pleasing for the driver, not raucous for the bystander.” Carrying PN 208.50.4800, this particular system fits all 1997-2004 Corvettes; MSRP is $1,395.00.
02. This stock Z06 exhaust...
02. This stock Z06 exhaust isn’t dirty, it’s made from titanium – very cutting-edge for 2001, and actually its first application on a mass-produced car. In addition to purportedly flowing a bit more than that of a standard Corvette, the Ti cat-back’s main advantage is that it is lightweight, said to come in at just 26 pounds. Ours inexplicably hung quite a bit crooked, hence the band clamp on the passenger side.
Such a good find naturally opens up some spare change for upgrades. The fact that this is a first-year Z06 means its 385-hp LS6 is slightly down on power compared to the ‘02-’04 model years (which received upgrades in the form of a bumpier cam and complementary lighter valves, improved airbox and MAF, and a less-restrictive catalytic converter setup, adding 20 hp to the advertised SAE figure). On the Dynojet at Heintz Racing (Mooresville, NC), a baseline pull resulted in 330.5 hp and 329 lb-ft, which equates to roughly 389 horsepower at the flywheel if you assume 15% drivetrain loss - about right, considering this car already had an aftermarket air filter. According to the Heintz crew (full-service specialists in late-model GM, Ford, and Chryslers), later C5 Z06’s normally put about 345 ponies to the tires…. could this deficiency be made up by simple swaps of an intake and cat-back?
It sure can. Beyond our dyno-proven increases, real-world performance shot up as well. Before-and-after HPDE track events at Virginia International Raceway proved the added underhood potency, as 140 mph was easily eclipsed on the back straight (the car was just able to touch that figure before). In addition, your Bondurant-trained author felt no discernible difference in handling due to the added mass of exhaust hanging behind the rear axle.
03. Removing the cat-back...
03. Removing the cat-back is a simple matter of disconnecting two bolts at the start of each over-axle pipe. Of note: the factory H-pipe upstream isn’t titanium. Rather, it’s steel; hence the bit of corrosion.
04. With the antiroll bar...
04. With the antiroll bar mounts disconnected from the Vette’s aluminum subframe, Jeff Heintz slides the Ti exhaust out of the hangars under the bumper, and each side comes out as one piece. To verify GM’s claims, we pulled out our scale and weighed the exhaust: the display showed 27.2 lb, proving pre-bankruptcy GM to be chock full of lies (either that, or there was a pound of residual water trapped in the muffler packing – you be the judge).
05. The new, beautifully...
05. The new, beautifully polished over-axle pipes are rested atop the axle assembly. There is a LH and RH pipe here, and Callaway is kind enough to label the bags they are shipped in - each pipe in the system comes individually wrapped, a nice touch. (Side notes: the L-shaped brackets just aft of the subframe are discarded; apparently this car had an aftermarket cat-back at some point. Jeff spots a stock plastic antiroll bar end link on the driver side; they are breakage-prone so he swaps it out for an updated metal piece.)
06. Callaway specifies reuse...
06. Callaway specifies reuse of the stock bolts, and also opts not to supply new gaskets, so Jeff improvises with some RTV silicone. The bolts get 37 lb-ft (no need to wait until the rest of the exhaust is up to final tighten).
07. The 90-degree elbow pipes...
07. The 90-degree elbow pipes go onto the back of the over-axle pipes, then the driver side muffler is slid on. A total of six band-style exhaust clamps are provided; the smaller-diameter ones are used here, two of which can be seen hanging freely at the moment. Jeff positions a screw jack in order to help hold the muffler while the tip assembly goes on.
08. The tip assembly slides...
08. The tip assembly slides into the driver side muffler (use a larger-diameter clamp for this junction), then the passenger side muffler can go on. The tips are centered and leveled, and the mufflers angled to follow the lines of the rear fascia, before all clamps are tightened. The one-piece tip assembly (“Double-D pipe”) is an unusual look for a C5, but we’ll never have crooked exhaust tips! While Callaway sells an exhaust tip surround panel to fill in the gap around the tips, I dig the view of the shiny pipes from behind. The weight of this exhaust is a good bit more (~24 lb) compared to the stock Ti, but at least it’s down low and in the rear.