[Editor’s Note: This LS1 engine upgrade guide is the first in a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing. The LS1 engine is a Gen III 5.7L aluminum-block V8 car engine that first appeared in the 1997 Chevrolet Corvette. The LS6—introduced for the 2001 Chevy Corvette Z06—is also a Gen III 5.7 aluminum-block V8. While the LS6 emerged from the factory with more power than the LS1, both engines can make the same power with common upgrades. You’ll see plenty of LS6 references below as a result. For a primer on the LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]

Intro to LS1 Upgrades

On a stock LS1 engine, the following upgrades can improve performance and fuel economy:

A stock LS6—a Gen III 5.7L aluminum block V8, just like the LS1—has more power than a stock LS1, but both can make the same power with common upgrades.

[Every engine spec you’ll need for an LS1 project can be found here: LS1 Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More.]

The aluminum blocks are not as strong as the LS-based iron-block Vortec truck engines like the LQ4 and LQ9, but both the LS1 and LS6 can be pushed to over 850 horsepower with upgraded internals.

If you’re on the hunt for the best mods for your LS1 engine, you’re in the right place. Here’s the path to upgrading your powerplant to achieve maximum performance.

(Summit Racing’s Paul Spurlock contributed to this article.)

Upgrading the LS1 Intake Manifold and Throttle Body

  • If you have an LS1, upgrading to the LS6 intake is inexpensive and popular.

The throttle body diameters are identical. Aftermarket intakes can produce strong gains with a 90mm (LS2) throttle body. Short-runner intakes are better from 5500 rpm and up. Long-runner intakes make more power through the entire range. These are generally better for cars with stock gearing and a mild converter.

  • When changing intakes, take note of the throttle body and the number of bolt holes in the mounting flange.

F-body cars and the 2004 GTO were cable-operated. The Corvettes came with electronic throttle control (drive-by-wire).

LS1 and LS6 throttle bodies were both 78mm and had a three-bolt mounting flange. Aftermarket manifolds usually have a four-bolt flange.

  • If hood clearance isn’t an issue, tunnel rams produce big gains at 6,000+ rpm.

Single-plane intakes don’t make as much torque or power as the tunnel rams. But, for engines turning 5,500+ rpm (minimum), or are subject to nitrous backfires, they begin to make more sense.

[Trying to find an LS engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.]

Upgrading the LS1 Fuel System and Tuning the Engine

  • Fuel injectors: The standard 28-pound injectors only support about 390 hp at 90-percent duty cycle. Upgrading to larger injectors is required if you’re planning more power.
  • Fuel pumps: The factory pump becomes a limitation at 450 hp. Drop-in dual pumps are a common upgrade.

Custom tuning will be required to properly adjust the fuel and ignition systems.

Because of the popularity of LS upgrades, chassis dyno tuning with the factory ECU is most common.

Upgrading LS1 Cylinder Heads

The LS1 heads were good, but the LS6 heads were better. Both respond well to custom machine work:

  • Porting: CNC-machined factory heads (LS1 or LS6) can flow over 320 cfm.
  • Milling/Decking: Without modifying the intake manifold, LS1 heads can be taken to 62cc chamber volume. The LS6 can be taken down to 60cc. This will create up to 11:1 compression on pump gas. However, be aware that piston-to-valve clearance will be reduced.
  • Aftermarket cylinder heads offer a range runner and chamber volumes. Additional deck thickness helps head gasket sealing with power adders.
  • Lightweight LS3 valves can be cut to fit the seats.
  • Performance valve springs will reduce valve float.

four-corner steam kit can reduce hot spots that cause #7 piston ring gaps to butt.

Upgrading the LS1 Camshaft and Valvetrain

  • LS engines respond extremely well to cam swaps.

Just match the other parts you choose to support it. This isn’t just valve springs and rockers. It includes intake, heads, exhaust, torque converter, rear-end gears, etc.

  • The trunnion bearings in the stock rocker arms are another known weak point. 

Retrofit trunnion kits fix this. Upgrading to full roller rockers is recommended for over 0.600-inch lift.

Upgrading the LS1 Rotating Assembly

  • The stock pistons are a known weak point.

As horsepower increases, so does heat. The stock cooling system wasn’t designed to handle the added heat.

The excess heat can cause the top piston ring to expand. Under enough heat, it will close the ring gap and the ends will butt together. When they do, a broken ring land can result.

Broken ring lands can happen with as little as 450 hp in road racing, or 600 hp in drag racing.

  • Another weak point of the stock pistons is that they don’t have valve reliefs.

This will limit piston-to-valve clearance. A set of forged pistons should be high on your priority list.

  • 1997-2000 LS1 connecting rod bolts are another weak point.

In 2001, the LS1 used the stronger LS6 bolts.

Rods with the 2001+ bolts are good to 500 hp and 7,000 rpm (naturally aspirated). With boost or nitrous, 700+ hp can be achieved if rpm is limited to 6,500.

The stock crankshaft can handle about 900 hp and 7,000 rpm (for a limited time).

Stroker cranks also add extra displacement. If rods and pistons are replaced, it makes sense to upgrade the crank at the same time.

Performance balanced rotating assemblies make the job easier.

Upgrading the LS1 Engine Block

The 1997-1998 LS1 blocks had thin cylinder sleeves. Honing them 0.005-inch oversized is the safe maximum.

Later blocks had thicker sleeves that can be honed 0.010 inch.

  • Upgrading to a four-inch stroke ups the displacement to 383 cubic inches or 6.3L.

Another way to increase displacement is to re-sleeve the block.

Generally, the 1999-2000 LS1 block is the preferred starting point. It has solid main webbing and better rear oil galley passage than the earlier blocks. The 1997-1998 LS1 blocks have solid main webbing, but less desirable oiling.

  • LS6 blocks are not good candidates for re-sleeving.

These blocks have windows cast into the bulkheads for improved breathing. When machining for larger liners, there is less material to support the cylinder which results in a weaker engine block.

  • Using the proper sleeves, the bore can be increased to 4.125 inch, and with a four-inch stroke, the displacement increases to 427 c.i. or 7.0L.

With boost, sleeved blocks have been pushed to over 2,000 hp. These blocks have added bracing, oiling upgrades, and provisions for six head studs per cylinder.

(Information for this article originally appeared in this Upgrading the Gen. 3, 5.7L, LS Car Engines article at Summit Racing’s searchable database of FAQ tech info. Go there and search “LS engines” for a comprehensive collection of LS engine tech information.)

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.