Making Sense of LS Engine Codes

So, you want an LS, you NEED an LS. LS is love; LS is life! But as the time comes to load the tools into the truck and hit that boneyard, the question suddenly arises: “Which LS engine is right for me? And what do all these codes mean?”

What are LS engine codes and why do they matter?

The term “LS” comes from the RPO code given to them by GM. “RPO stands for Regular Production Option and is General Motors’ standard coding for vehicle configuration options,” explains New GM Parts, a specialized wholesale distributor of genuine GM OEM replacement parts and accessories. “Each RPO code is a combination of three alphanumeric characters (like Z71) that refers to a specific option or modification to the vehicle as built during production. The RPO codes identify the base model of the vehicle along with options such as paint color, engine, infotainment system, wheels, etc…”

However, when it comes to LS engine codes, there exists some controversy among the masses. LS engines are built on the small-block platform and, because of this, they share many characteristics with Gen 2, Gen 3, and Gen 4 engines in this category. The problem? A lot of people will loosely define non-LS engines as LS engines.

This typically comes from those using earlier-generation small-blocks or engines sourced from trucks and simply calling them an LS to keep confusion at a minimum. It’s just easier to say “Oh yea, it’s an LS,” instead of saying “Well, it’s a lot like an LS but there are some differences…”

So, even though the LS engine family is limited to vehicles denoted LS1, LS3, LS6, etc…, this leniency squeezes a wide range of engines and codes into the realm of the LS family. Knowing and understanding what these codes mean and how they differ will help you determine what LS engine you’re looking at while you sift through junkyard treasures, saving time and money.

What LS Engine Do I Have?

To figure out what LS engine you’re staring at, just consult the RPO code. The easiest way to do this is to find the VIN and reference the 8th digit. The tables below can help you identify the engine.

Which LS Codes Do I Want?

Depending on who you talk to, this answer will vary. Suffice it to say, there are a lot of great LS engines, but budget and market demand are really going to determine what you can get your hands on. The important thing is to keep your build goals in mind.

For example, if all you want is reliability and some power and a 4.8L is the most affordable option, then that’s probably the best option for you. Keep in mind, the 4.8L engines often make just as much or even more power than the older and often larger V8s that they replace—so size isn’t always everything. Although, neither is price. Just about every seasoned LS builder will tell you the importance of buying the most complete engine you can afford—not merely the cheapest. Otherwise, the odds and ends are really going to stack up against you.

There’s no way around it: LS engines are very desirable and that often drives up cost. While they still exist within the realm of affordability, more often than not owners will ask a premium price—especially if they know they’re sitting on something special. Check out our guide on sourcing LS engines for some tips and tricks when purchasing from junkyards or private sellers.

How much are you willing to spend?

That said, the LS9 and LSA engines are often the most extreme, as they can draw in prices of nearly $10,000 used on account of the supercharger. 5.3Ls, 6.0Ls, and 6.2Ls typically run $1,500 – $3,000, while several 5.7Ls can creep into the $5k range. Generally speaking, 4.8s will draw in the least amount of money (likely a few hundred dollars in most cases) but the LY6 also offers some bang for your buck. It usually runs pretty cheap and its bore size makes for a quick process when chasing power. The YouTuber in the video below explains that the LS4 and LQ4 also fall into this realm of potential, but because they are well-known, they’ll run a little higher in price.

If you’re seeking something that’s already powerful, your top choices will be the larger displacement engines: 6.0L and 6.2L. These engines are already turning out well over 300 hp so if that’s good enough for the time being, all that’s left to be concerned with is getting it into place.

If you’re building an LS though, you’ll find more debate.

Our friend John Potucek of Keystone Automotive, who we often turn to in times of such LS deliberation, leans toward the L33, a beefy but rare option that had a limited run from 05-07. “This is often referred to as the ‘factory race engine’ among my friends,” he says. “It’s an aluminum block 5.3L, flat top pistons with Gen4 internals and good flowing heads. Some people are scared of the aluminum block, thinking it’s too weak—but that’s false. The 5.3 has nice thick walls and is constantly being used in 1000-hp applications.”

John’s point on the 5.3 having thick walls is important to remember as you consider what you want from your engine. This engine’s boosted reliability, paired with its abundance and affordability are contributing factors to why so many builders choose it. If you’re wondering why anyone bothers to opt for 6.0s and 6.2s if the 5.3 can turn out 1,000 hp, the answer is because the larger displacement engines can hit that number much easier—yet another factor to consider when you’re leveraging your budget against your build plans and, ultimately, skill set.

Remember: many of the aftermarket parts for LS engines are interchangeable regardless of displacement. Intakes, exhaust, cams, and even boost solutions generally cost the same regardless of the engine. 

You Do You

It’s worth repeating: The best LS engine for you is the most complete one you can afford. Sometimes that’s a cheaper option with moderate power, and sometimes it’s a big beast with inherently big power. The LS engine, in general, is largely affordable and easy to modify, so in many cases, whatever you can start with is good enough.

Even if you find yourself digging through junkyards and classified ads, deciphering LS engine codes and crunching your budget, remember that the whole reason everyone loves this platform is because of its potential. Focus on where the engine can go, not exactly where it’s starting out. So what if you can only afford the “less desirable” LS? You’re still in great shape to build something totally unique.