How we spec different LS power levels

The GM LS engine family is one of the most popular engine platforms in the world, and for good reason. LS engines are compact, strong, widely available and supported by a huge aftermarket. But one of the most common questions we get is also one of the hardest to answer: what parts do I need for my LS horsepower goal?

This article explains how we at Blenco Speedshop generally think when we spec LS engine combinations for different power levels. It is not intended as a universal rulebook, a guarantee or a final answer for every build. Engine durability always depends on the complete combination, machining, clearances, tuning, fuel system, oiling, rpm, boost pressure, intended use and how the engine is actually driven.

In other words, this is not the only way to build an LS engine. This is how we reason when choosing parts for different LS power levels based on our experience, the parts we trust and the type of use the engine is built for.

Before Choosing Parts, Define the Real Goal

A 700 hp street engine, a 700 hp drag engine and a 700 hp marine engine are not the same thing. The horsepower number matters, but so does rpm, boost, torque, fuel type, vehicle weight, gearing and how long the engine will be under load.

For example, a turbo street car that makes one short pull at a time is very different from a boat engine, a road race engine or a heavy truck that sees long periods of load. This is why we do not like choosing parts only from a horsepower number. The full application matters.

Stock Gen III LS Internals, Around 500 Crank HP

A stock Gen III LS engine, such as an LM7, can be a very good starting point for a budget build. However, we do not recommend treating stock Gen III internals as a high rpm or high boost foundation. In our opinion, around 500 crank horsepower and approximately 6,500 rpm is a sensible limit for many stock Gen III based combinations when reliability is still important.

This same general thinking applies to many stock LS car and truck engines. Stock Gen III internals can work well at moderate power levels, but once the build starts moving toward more boost, more rpm and harder use, we prefer upgrading the rotating assembly rather than pushing stock parts too far.

At this level, the right camshaft, valve springs and supporting parts can make a big difference. A camshaft should always be chosen for the application, not just for sound.

The valve springs must also match the camshaft. For mild setups, an LS6-style valve spring can often be a simple and useful upgrade. For more aggressive camshafts, higher lift and higher rpm, the spring package becomes much more important.

Budget Upgrade, Gen IV Rods and Pistons, Around 700 Crank HP

One of our favourite budget upgrades for an early LS engine is upgrading to Gen IV rods and pistons. In our opinion, a good Gen IV rod and piston combination can be a very cost-effective setup for approximately 700 crank horsepower and around 7,000 rpm, assuming the rest of the build is correct.

This is not a magic limit, and it is not a guarantee, but it is a level where we have much more confidence than with early stock Gen III parts. It is a strong budget combination for many street and performance builds.

At this level, the piston rings do not necessarily need to be exotic. What matters is using a good quality ring set and gapping the rings correctly for the intended use, especially if the engine will see boost, nitrous or high cylinder pressure.

Camshaft, Springs, Trunnions and Timing Set

Even when the bottom end is kept relatively simple, we usually prefer replacing the camshaft with something better suited for the application. The camshaft should match the compression ratio, cylinder heads, intake, exhaust, converter, gearing, boost system and intended rpm range.

The springs must always be matched to the camshaft. If the spring package is intended for more than approximately .580 inch lift, we also recommend upgrading the rocker arms with a trunnion bearing upgrade. This is a small upgrade compared to the total cost of the build, but it adds security in an area that is often overlooked.

For a mild LS6-style spring and moderate camshaft setup, a stock type timing set can be perfectly acceptable. But once the camshaft, spring pressure and rpm increase, we prefer upgrading to a stronger aftermarket billet style timing set.

Middle Ground Setup, LT1 Rods and Forged Pistons, Around 800 to 900 Crank HP

A good step up from the budget Gen IV setup is a middle ground combination using LT1 rods, preferably with new ARP rod bolts, paired with a good set of forged pistons. This can be a very nice street and performance combination when you want more safety margin without going all the way to a full aftermarket race rotating assembly.

At this level, we also prefer using ARP head bolts or head studs, depending on the application. A quality head gasket is also recommended, especially if the engine will see boost or higher cylinder pressure.

For a street car at this level, a 4032 aluminium forged piston can be a very good choice. It allows a tighter piston to wall clearance than a typical 2618 race piston, which can help reduce noise and improve long-term street manners. For many street engines that need to live many miles, this is a very useful piston material.

In our opinion, this type of combination can be suitable for approximately 800 to 900 crank horsepower when the full setup is built and tuned correctly.

Aftermarket H-Beam Rods and 2618 Pistons, Up to Around 1000 Crank HP

The next step in our opinion is moving to a proper aftermarket forged H-beam connecting rod and a forged piston. We use a lot of Callies Compstar rods, but most quality brands have good options in this category.

At this level, we usually recommend a 2618 aluminium piston, especially for boosted, nitrous or high output applications. We run a lot of Diamond Competition Series pistons for this type of build because they are a proven option for serious LS combinations.

At this power level, we also recommend using ARP main studs, ARP head studs and a Melling Performance oil pump. The head gasket also becomes more important. Depending on the engine and application, we would usually look at an LS9-style head gasket or a Cometic MLS head gasket.

In our opinion, this is the type of combination we would usually advise for a maximum of around 1000 crank horsepower, depending on the full engine specification.

Forged Crankshaft, Upgraded Pins and Better Heads, Around 1200 Crank HP

Many people continue to run a stock LS crankshaft past 1000 horsepower, and it can work in some combinations. However, once we move beyond this point, our preferred next step is a forged crankshaft, upgraded wrist pins and a better cylinder head package.

At this level, we prefer upgraded wrist pins, preferably tool steel pins with approximately .200 inch or thicker wall, depending on piston design and application. The piston, pin, ring package and cylinder head choice should all be matched to the intended boost, rpm and cylinder pressure.

In our opinion, this type of setup is a better direction for builds around 1200 crank horsepower.

CCW Crankshaft, Better Rods and Stronger Head Fasteners, Around 1500 Crank HP

The next step is where the details become much more important. At this level, we prefer an aftermarket CCW crankshaft. A CCW crankshaft has an additional counterweight in the centre section, which improves balance and can help reduce the tendency for main cap movement. Main cap movement can quickly lead to bearing wear and serious engine damage.

At this level, we also recommend a stronger connecting rod package. Good examples include Callies Compstar Xtreme or Wiseco BoostLine connecting rods. This is also the point where stronger head fastening becomes very important.

Around this point, we also recommend looking at some form of hoop system. That can mean mini hoops with an MLS gasket, or a more traditional hoop setup with a copper head gasket depending on the build. The purpose is to improve combustion sealing when cylinder pressure becomes very high.

This is also where a stock LS block can become a real risk. A stock block can live at high power in some cases, but if something goes wrong, it can also fail very quickly. In our opinion, around 1500 crank horsepower is where everything needs to be taken very seriously, especially if using a stock block.

Aftermarket Block, Dart SHP LS Next, Safer 1500 HP Level

The next level is moving to an aftermarket block. At this point, the build becomes much safer and more future-proof. A Dart SHP LS Next block is a strong step up from a factory LS block while still allowing a very usable and familiar LS-based combination.

With the right internals, this is still broadly a 1500 horsepower level combination, but the important difference is safety margin, long-term reliability and upgrade potential.

Dart SHP Pro LS Next, Billet Crank and Higher Level Pistons, Around 1800 Crank HP

The next step is a stronger block package, such as the Dart SHP Pro LS Next. At this level, we also want a very high quality crankshaft, such as a Dart billet crankshaft, Brodix billet crankshaft or Callies Apex crankshaft.

The piston package also needs to move up a level. A piston such as a Diamond LS2K is more appropriate for this type of cylinder pressure and horsepower target.

In our opinion, this is the type of package we start looking at around the 1800 crank horsepower level.

Around 2000 Crank HP, Better Rods, Real Hoops and 1/2 Inch Head Studs

For a build around 2000 crank horsepower, the connecting rod becomes even more critical. At this level, we would move to a stronger rod such as a Callies Ultra Enforcer or another connecting rod in the same serious power category.

A real hoop system and 1/2 inch head studs should also be considered mandatory at this point in our opinion. Cylinder pressure is extremely high, and combustion sealing must be treated as one of the most important parts of the build.

Beyond 2000 HP, Bigger Block Architecture and Cleveland Mains

After this point, the next real step is upgrading the block again. For very high horsepower LS-based combinations, we start looking at blocks with more material, stronger main webbing and Cleveland main bearing architecture. The larger main bearing and larger thrust bearing help add strength where the engine needs it most.

At this level, we want at least a Callies Magnum crankshaft and a custom piston package, often based around a custom Diamond piston. You can still use a very high quality steel connecting rod such as a Callies Enforcer style rod in some combinations, but if the engine is intended to run 9,000 rpm or higher, rod bolt quality becomes even more important.

For extreme rpm and serious race use, we may recommend upgraded rod bolts or moving to MGP aluminium connecting rods, depending on the application, service interval and intended use.

At this point, a really good cylinder head package is also required. The cylinder heads, intake manifold, valvetrain, camshaft, lifters, pushrods and oiling system all need to be treated as part of the same complete race engine package. There is no single part that makes an engine reliable at this level. The whole combination has to be correct.

Quick Summary of Our LS Power Level Thinking

General Lifter, RPM and Oiling Guidelines

For moderate camshaft and spring combinations, we usually run the Delphi-style LS lifter from either BTR or Straub. These have proven to be a reliable option for many street and performance builds.

Once we move into approximately .660 inch lift spring territory, we recommend stepping up to a better hydraulic roller lifter such as the Morel 7717 drop-in lifter.

If the plan is to rev beyond roughly 7,200 rpm, we typically move to the Chevrolet Performance Caddy Race lifter. For combinations targeting 7,500 rpm and beyond, we generally recommend an Isky/Johnson medium-travel link-bar lifter.

At 8,000 rpm and above, our preference is usually a solid roller camshaft setup. In some applications, a short-travel hydraulic roller lifter can still be used when there is a specific reason to retain a hydraulic camshaft.

Once you are operating consistently in the 8,000 rpm range and beyond, we also strongly recommend a dry sump oiling system. At that point, oil control becomes a major factor in both reliability and performance.

Final Thoughts

The LS platform can support an incredible range of power levels, from mild street engines to extreme race combinations. But the higher the power level, the more important it becomes to stop thinking about single parts and start thinking about the complete engine system.

Rods, pistons, crankshaft, block, head studs, head gaskets, cylinder heads, camshaft, valvetrain, oiling, fuel, tuning and machining all need to work together. One weak link can quickly become expensive.

At Blenco Speedshop, we only sell parts and combinations we believe in. We are happy to help spec an LS build based on your engine, your horsepower goal and how the car, boat or project will actually be used.

Contact us about your LS build