Upgrading the LS2, L76, and L77 Engines

The aluminum block, 6.0L engines are light and durable, with many options for increasing power. On a stock engine, the following upgrades can improve performance and fuel economy:

• A Cold Air Intake Kit
• Headers
• An Aftermarket Exhaust
• A Computer Programmer

Below are more upgrades that will improve the performance of the LS2, L76, L98, and L77 engines.

Engine Block

These engines share a 4.000 in. bore diameter. The cylinders can be bored to 4.030 in. However, we recommended leaving them as thick as possible when running boost. When bored and stroked, displacement can be as high as 408 c.i.d. (6.7L).

The block can handle 850 to 1000 horsepower. However, you will want to upgrade to Head Studs and Main Studs if you plan on using boost or nitrous.

Rotating Assembly

The stock pistons are a known weak point. They will crack in high horsepower engines. A set of Forged Pistons should be high on your priority list. When stroking, choose a piston with minimal skirt taper. This prevents the piston from rocking at BDC and scraping up the skirts.

Gen. 4 rods are stronger than the Gen. 3's and have full floating pins. They can handle about 800 hp. and 6,500 rpm in boosted applications. If you're getting forged pistons, upgrade to Forged Connecting Rods at the same time.

Even though it’s cast, the crankshaft can handle about 900 hp. and 7,000 rpm (for a limited time). A broken crankshaft is bad news. Upgrading to a Forged Crank early in your build will save you the headache later. When you upgrade, a 4.000 in. stroke crankshaft costs about the same and increases displacement.

The chart below lists standard specs compared to common performance Rotating Assemblies.

Cylinder Heads

The LS2 has cathedral port cylinder heads which can be CNC ported for more airflow. The heads can be milled for more compression. However, compression on these engines is already in the high 10:1 range. You don't want to go much higher when running pump gas. For high rpm engines (7,000+), LS3 intake valves are lighter and can be cut to fit.

The L76, L98, and L77 heads have rectangle intake ports, like the LS3/L92 heads. Light weight, hollow stem intake valves from the LS3 drop right in for high rpm use. They can be CNC ported for better air flow. It is also common to mill them up to 0.030 in. to increase compression.

There are many Aftermarket Heads available. The heads flow better and have thicker decks to maintain head gasket seal. A wide range of runner and chamber volumes are available. Some also go from a 15 degree to a 13.5 degree valve angle for even more power.

A 4-Corner Steam Kit is another smart upgrade. It reduces hot spots in cylinder #7 that cause the piston rings to butt and crack the piston.

Camshaft and Valvetrain

LS engines respond well to Cam Swaps. In addition to valve springs and rockers, the cam needs to match the compression, torque converter, rear-end gears, etc. Keep in mind, piston-to-valve clearance is tight with cams over 230° duration @ 0.050 in.

Spring Kits are available for typical 0.600 in. lift cam upgrades. Titanium retainers are another upgrade that will reduce

The trunnion bearings in the stock rocker arms are another known weak point. A Trunnion Upgrade Kit should be installed when you upgrade the valvetrain. Upgrading to Full Roller Rockers is another option.

The stock rockers are pedestal mounted. High spring pressure (over 475 lbs.) can pull the bolts out of the cylinder head. Converting to roller rockers and stud mounts is recommended for cams over 0.600 in. lift.

Many of these engines were equipped with Active Fuel Management (AFM). It's good for gas mileage, but not high performance. If the valvetrain is in good condition, an AFM Disabler can turn the AFM off. When upgrading to a performance cam, an AFM Delete Kit is strongly recommended. These kits replace all the AFM components with standard parts.

Switching from a 1-bolt to a 3-bolt cam is a popular option, when removing AFM and/or VVT components. Just make sure you get the timing set with the correct number of poles for your cam sensor. Most people use either a 1X, 2005 Corvette Gear or 4X, 2006 Corvette Gear.

Intake Manifold and Throttle Body

The stock LS2 intake did not flow as well as other manifolds. We recommend an Aftermarket Intake. The rectangle port intakes flowed better than the LS2. But, an aftermarket intake can still make more power. Just make sure to match the intake port shape on the heads.

At 90mm, the factory 4-bolt throttle body is fairly large and won't be a restriction in most applications. Most aftermarket intakes are designed to accommodate larger 102mm Throttle Bodies.

Something to watch out for on these engines is the direction of throttle blade rotation. Throttle bodies with a silver blade rotated one way. Gold blade throttle bodies rotated the other way. Verify you are using the correct one for your computer.

Power Adders

Many Supercharger Kits are bolt-on and work with stock internals and pump gas. More serious kits are available, but will require internal upgrades.

Nitrous Kits are also available, inexpensive, and easy to install. Street kits have lower settings that work with stock internals. More power requires higher settings and upgrading the engine internals.

Fuel System and Tuning

Upgrading to larger Fuel Injectors is often needed to meet the demand of increased power. The factory fuel pump will become a limitation around 400 hp. So, plan on upgrading the Fuel Pump as well.

Truck engines have a conservative tune from the factory. Tuning the computer changes the fuel and ignition curves to increase performance. Plug-In Programmers are easy to use, but they do have limits. Custom tuning requires more knowledge, but will provide even better performance.