Chevrolet Corvette C5 Z06 Performance Upgrade Guide

The LS6 engine powered the C5 Z06 Corvette and the CTS-V. With the C5’s being popular track and street cars, there is a ton of aftermarket support for these engines. And fortunately, there are some easy bolt-on modifications that can push you right up to the 500hp limit of the factory internals.

In this guide we’re going to discuss engine power limits and then jump into thermostats, cold air intakes, headers, intake manifolds, upgraded camshafts, and tuning. Our goal: teach you how to build a reliable LS6 pushing around 500hp.

LS6 Engine Power Limits

Staying naturally aspirated and around the 500hp mark is about the safe limit for the factory internals. When you start adding forced induction, through superchargers or turbochargers, the internals start to become more suspect.

The engine block is good until around 800 horsepower, while the pistons and connecting rods are limited to ~500 horsepower (and 7,000 rpm). Upgrading to forged internals will allow for more horsepower and rpm, and should be done on builds surpassing 500 horsepower. 

Corvette C5 Z06 Performance Mods

• Colder Thermostat
• Cold Air Intake
• Long-tube Headers
• Upgraded Intake Manifold
• Upgraded Camshaft
• ECU Tuning

1) Thermostat Upgrade

A thermostat upgrade is a cheap and easy mod to increase performance, and is very beneficial to owners in hot climates. The purpose of a thermostat in a car’s engine is to regulate the engine’s operating temperature. They are designed to keep an engine operating within a specified temperature range. 

Here’s how thermostats work. While the engine is still cold, the thermostat stays closed and keeps the coolant circulating within the engine block. After the engine reaches the minimum specified temperature, the thermostat opens and allows the coolant to flow into the radiator. The radiator’s job is to reduce the temperature of the coolant, so it can re-enter the engine to cool it and keep it operating within its optimal range. The thermostat constantly alters the flow of coolant in and out of the engine to regulate the temperature. 

2) Cold Air Intake Upgrades

Upgrading the factory air filter and tubing will increase air flow and velocity, reducing restriction and improving performance. By themselves, an upgraded C5 Z06 intake won’t gain tons of power. But when coupled with our other mods like long-tube headers, an intake manifold upgrade, and potentially forced induction, they will help unlock more performance. 

On the Cadillac CTS-V, a performance intake is a much better mod. Due to the more traditional layout of the engine bay, a cold air intake can be a solid upgrade due to the upgrading of the filter and tubing.  

3) Long-Tube Headers

Compared with OEM, long-tube headers have wider diameter piping and a less restrictive design that is optimized for performance. This reduces the back pressure between the headers and the engine, which allows for much faster exhaust flow. Faster exhaust flow means more horsepower and torque. On the CTS-V, long-tubes will produce up to 25 horsepower and torque. On the C5 Z06, long-tube headers will produce closer to 15 horsepower and torque due to the less-restrictive factory exhaust. 

Importantly, when upgrading to long-tube headers on the C5 Z06 or CTS-V, you have to be aware of emissions laws. There are both catted and catless versions of long-tube headers, and high-flow catted ones are what you will most likely want. Catless headers are for track and race use only, meaning they are not street legal. However, high-flow cats offer very similar performance, and smell much better, and are the only legal options. 

4) Intake Manifold Upgrades

The LS6 intake manifold is already one of the better ones from the factory. In fact, it was good enough that Chevy decided to retrofit it to the earlier LS1 engine starting in 2001. 

The intake manifold is the last step in the intake chain before the air reaches the engine. On the front is the throttle body which takes in air from the intake, and the manifold sits directly on top of the cylinder heads. Aftermarket intake manifolds offer superior flow characteristics than the stock manifold, and they are ideal if you are planning on running forced induction.

To learn more about the performance benefits and manifold upgrade options, read our LS6 intake manifold upgrade guide.

5) Camshaft Upgrades

The camshaft is part of the valve train, and the LS6 uses an overhead valve train (OHV) with a single in-block camshaft. The LS6 inside the C5 Z06 used two different profile camshafts during its production run. For 2001, the LS6 used a cam that had an intake/exhaust duration of 204°/211°, with lift of 0.525”/0.525”, and a 116° LSA. From 2002-2005, the LS6 used a cam with an intake/exhaust duration of 204°/218°, with lift of 0.555”/0.551”, and a 117.5 LSA.

As you can see, the second LS6 cam was much hotter due to having more exhaust duration, greater lift, and a slightly wider LSA. The new hotter cam was partially responsible for the 20 horsepower and 15 lb-ft of torque increase in performance from 2001–2002 in the Z06. If you have a 2001 C5 Z06 a camshaft upgrade is a must, and on the 2002–2005 C5 Z06s they can still provide plenty of bang for your buck. 

To dig in deeper here, check out our LS6 camshaft upgrade guide.

6) ECU Tuning

There are multiple types of ECU tuning, and we recommend custom flash tuning. Flash tuning involves taking a handheld tuning device, plugging it into the OBDII port beneath your dashboard, and installing aftermarket calibrations. These calibrations optimize parameters like air-to-fuel ratios, ignition and camshaft timing, and fuel pressure, to provide the most horsepower and torque. 

The factory tune on the Z06 is actually already pretty good from Chevy, but it still prioritizes fuel economy and emissions over performance in many cases. An aftermarket tune will really allow the LS6 to operate at its full potential, without the restrictive factory tuning. If you have other mods, like the bolt-ons we listed above, tuning will allow for your engine to take the most advantage of the increase in airflow and air volume.  

Frequently Asked Questions