[Editor’s Note: This LS9 engine upgrade guide is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at OnAllCylinders. For a primer on the entire LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]

Intro to LS9 Engines

Although LS7 owners could put up an argument about which engine was greater, there is no doubt that the supercharged LS9 made more power than any production car—big or small block—before it.

The Gen. 4, 6.2L aluminum-block engine powered the Corvette ZR1 between 2009 and 2015. With 638 horsepower and 604 ft./lbs. of torque, the LS9 was not only powerful, but reliable.

To keep the ZR1 nimble, it was also light and compact, weighing 531 lbs. complete with manifolds, supercharger, clutch, flywheel, balancer, and water pump.

Built for performance, LS9 engines didn’t use Active Fuel Management (AFM), Variable Valve Timing (VVT), or Flex Fuel (E-85) technology. The materials used in the engine were of high grade and we’ll cover that further into the article.

[Every engine spec you’ll need can be found here: LS9 Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More.]

What can I do to get more power out of my LS9?

The LS9 engine makes a lot of power, but easily makes much more! Upgrades are usually done in stages. With the LS9, it usually starts with the bolt-ons and tuning, then blower upgrades. These alone can net 100 hp more than stock.

Things really get serious once we start upgrading the cylinder heads and camshaft. Then, finally, we’ll cover the bottom-end upgrades to withstand the added power.

Tuning and Bolt-on Upgrades for LS9

The upgrade path is straightforward, but it’s best to start with a baseline.

The first thing to do is speak with an established tuner with access to a chassis dyno. They will help you by choosing a programmer that they already have experience with.

A good tune can produce gains up to 40 hp on an otherwise stock engine. (Any significant upgrade will require re-tuning the computer.)

Adding a few bolt-ons before heading to the dyno makes sense and can be done in the garage. Here are some popular modifications:

LS9 Supercharger Upgrades

When introduced in 2009, the 2.3L R2300 TVS Eaton supercharger was the largest supercharger fitted to a production car in the modern era.

Its rotors were 8.3 in. long, 3.9 in. in diameter, and had a 160-degree helix.

It had a 2.32 drive ratio. It was fed by an 87mm throttle body and forced air through two intercooler bricks (instead of one as found in the LSA engine). The intercooler drops air-inlet temps by as much as 140 degrees.

With stock pulleys, the blower spins 15,800 rpm at redline.

The next step on the upgrade path is a pulley swap.

Spinning it harder and making more horsepower sounds pretty simple, but remember—with more horsepower comes more heat and the need for more octane. The chart below will give you some idea of what to expect.

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**If you change ONLY the upper pulley, you can still run premium pump gas. If you change both pulleys, you will need an octane booster.**

Increasing the speed of the supercharger will create more heat. You can lower the intake air temperature in several ways.

Note: Spraying water/methanol through your supercharger reduces lubricity and rotor life. There are services to coat the rotors and increase life.

Other Upgrades to the 2.3L LS9 Supercharger

Larger blower snouts can be fitted that accomodate larger throttle bodies, including those 102mm and larger.

There are other areas of improvement inside the blower. Internal restrictions starve the rotors of air. These can be removed through porting.

During the porting process, some will go as far as external welding to facilitate even more porting.

Upgrading the LS9 Fuel System

The LSA and LS9 engines share the same injectors and dual fuel pumps. The injectors effectively max out around 65 psi. The fuel pumps are controlled by a module that increases fuel pressure relative to boost. They start at 36 psi @ idle and ramps to 87 psi @ high rpm and full-throttle.

  • The injectors are rated at 52 lbs. @ 58 psi and good to about 600 hp at the wheels. Keep in mind, boost works against rail pressure, so pressure across the injector is lower at high boost.
  • The stock dual fuel pumps are good to about 650 hp at the wheels.

External fuel pumps can be plumbed to work in-line with the factory pumps. Using a signal from the MAP sensor, they know when extra capacity is needed and it will turn the pump on during periods of high load.

Supercharged engines love alcohol for cooling and the LS9 is no different.

There are bolt-on E85 flex fuel kits that serve as a plug-and-play solution. The programmer will allow you to unlock and populate the tables required to adjust fuel and timing to the alcohol percentage in the fuel.

Top-End Upgrades for LS9 Engines

The LS9 cylinder heads are upgraded versions of the LS3 heads. They were rotocast of A356T6 alloy for extra strength and received titanium intake valves and sodium-filled exhaust valves.

One downside was the addition of a flow vane in the intake port. While it helps emissions and idle stability, it comes at the expense of top-end power. It can be removed by CNC porting, and improvements of 70 cfm are common after doing so.

Aftermarket cylinder heads are another option. These heads will flow even better than ported stock heads and have thicker deck surfaces to withstand more boost. Another bonus is the reduced downtime and the original heads can often be sold to offset much of the cost.

Upgrading the LS9 Camshaft

Like other LS engines, a cam swap for the LS9 is a common upgrade.

The LS9 cam is one of the better cams from the factory, but there’s still a lot more power to be had.

Larger aftermarket cams can add up to 75 hp. Going as high as 0.630 in. of valve lift is also common and works with the factory rockers.

The table below gives some information on what to expect from different cams. (Note: We are assuming a standard blower, pulleys, tune, and standard pump gas.)

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Upgrading the camshaft will require the matching valve springs. Titanium retainers are also recommended.

The trunnion bearings in the stock rocker arms are a known weak point. We strongly recommend a trunnion upgrade kit.

Bottom-End Upgrades for LS9 Engines

The LS9 was chock full of the good stuff from the factory.

  • The forged pistons were dished without valve reliefs and weighed 546 g. with a 156-g. pin.
  • The titanium rods were more stout than the LS7 rods. Pin diameter was almost the size of a big block Chevy at .984 in. At 5.990 in. length, these full-floating rods weighed only 464-482 g.
  • The forged crank was made of manganese-vanadium steel with a 9-bolt flange and keyway.
  • 12mm head bolts were used instead of 11 mm as used on other Gen. 3 and 4 engines.
  • Special 7-layer head gaskets that offered more expansion if the head lifted.
  • Oil spray squirters to cool the pistons.
  • 9.1:1 compression ratio.
  • Forged steel main caps located with dowels.
  • Deck plate honed.
  • Dry Sump oiling with 10.5-qt. tank.

How do you improve upon something already so good? Cubic inches, of course!

Keep in mind, an aftermarket stroker crank will need the dry sump snout and 9-bolt rear flanged crank to remain compatible with the accessory drive and clutch.

While you’re at it, spend a few more bucks on a center-counterweighted crankshaft. The extra counterweights in the center add a little weight, but reduce the twist in the crank which results in uneven bearing wear.

The cylinders are usually honed 0.005 in. oversize and in .005 increments after that. This keeps the walls thick enough to support boost. A 4.000-in. stroke crankshaft will also increase displacement. The chart below lists the specs for a common bore and stroke combination.

Engine SizeBore Dia.Piston Comp. HeightStroke Rod LengthWristpin Dia.
6.2L (376 c.i.d.) stock4.065 in.1.443 in.3.622 in.5.990 in.0.984 in.
6.8L (416 c.i.d.)4.070 in.1.110 in.4.000 in.6.125 in.0.927 in.
7.0L (427 c.i.d.) aftermarket LSX4.125 in.1.110 in.4.000 in.6.125 in.0.927 in.
7.2L (441 c.i.d.) aftermarket LSX4.125 in.1.050 in.4.125 in.6.125 in.0.927 in.

Upgrading the LS9 Engine Block

The LS9 block was made from 319-T7 material. It had a unique part number because of the main caps, honing process, fasteners, etc.

What are the limitations? Even with the bigger head bolts, when you’re getting into the 1200+ hp territory, cylinder heads can lift from pressure spikes.

No problem, though.

You can solve this with six-head-bolt-per-cylinder aftermarket block.

NOTE: You can find engine specs and detailed engine upgrade advice for every LS and LS-based Vortec truck engine in one place: The Definitive Guide to LS Engine Specs and LS Engine Upgrades.

Author: Brian Nutter

After a stint in the U.S. Air Force, Brian Nutter studied at the Houston, TX-based School of Automotive Machinists in 1997. The early part of his automotive career included working for engine builders Scott Shafiroff and C.J. Batten, followed by several years developing performance pistons at Wiseco Piston Co. Today, Brian develops performance parts for Summit Racing Equipment and is a regular OnAllCylinders contributor. For fun, he runs his 427-powered C5 Z06 in ECTA land-speed racing, at OPTIMA® street car events, and at a mix of autocross, drag racing, and track days.