Previously Owned Gen III’s are the Big Winners in the Power-Per-Dollar Game

Words and Photos By Jeff Smith

It’s the hottest horsepower ticket in town – swapping LS power into an older street car. The idea certainly isn’t new; these swaps have been going on nearly from the moment the LS1 debuted in 1997. But there are a myriad of details to square away first before you decide to buy your first LS engine for transplant. A brand new LS3 right out of the box from Chevrolet Performance is tempting — Summit will sell you one right now for under $7,000. It’s tempting, but there are a few hidden costs for parts like an EFI harness, computer, electronic throttle pedal, accessory drive, and about a dozen other goodies that can easily push that price tag up over $10K.

That’s a big hit, which is why used LS engines are so alluring. For the rank and file, the deals are out there — but only if you know more than the guy who is selling. Our story is to give away the details on what’s hot. Depending on your goals, there are great deals to be had — especially if you know exactly what you’re looking at. The wag has always been “knowledge is power.” That’s no more true than with all the LS engine variables.

This story will concentrate on the most affordable, first generation used LS engines — the Gen III engines with a few Gen IV details dropped in to keep you up to speed. Gen IIIs were used in the GM family of cars and trucks from the original LS1 in the Corvette in 1997 through 2006. We’ll also toss in a few recommendations on the Gen IV engines, essentially the rectangle port engines that also came in both trucks and cars. But, we will mainly focus on the Gen III engines because they are the most affordable. And while many enthusiasts may disagree, there are many situations where a cathedral port style engine is a better choice over their rec-port cousins.

Perhaps the best place to start when searching for a good LS street engine is to first decide how the engine will be used. We will focus on normally aspirated engines. We will toss in a couple of examples of power adders and how fantastically they work on LS engines, but mainly we’ll keep to the normally aspirated side of things.

Being true to the direction your engine selection will go is a critical decision for multiple reasons. For example, if your goal is simply to make the most horsepower for a drag strip hero effort, then maximizing displacement is a smart move. But, if your desires are more conservative, then don’t be swayed by the forum dwellers who will dismiss the “little” 4.8L and 5.3L engines as to be avoided. Our experience has been quite the opposite. A little later, we’ll outline an example where we’ve tweaked a “runt” 4.8L truck engine to make more than 375 hp.

We should probably start with a general overview of the different displacements the Gen III family offers, starting with the smallest and working our way up. While the Corvette first offered the 5.7L in 1997, by 1999, all GM trucks were using LS engines. The base V8 began life as a 4.8L (293c.i.) engine with a small bore and 3.26-inch stroke. This iron block truck engine has been universally overlooked and, as a result, can be very inexpensively purchased. Our best deal was a 4.8L motor with no accessory drive and no intake for $350, but we have friends who tell us in the Midwest, you can find these little motors for little more than the price of hauling them away.

The next step up is the truck 5.3L. You can think of this engine as a 21^st Century version of the venerable 327 small-block. The difference is it uses a smaller bore and longer stroke, but makes excellent power and will be the easiest engine to find on the used market because GM has built more 5.3Ls than any other single LS engine.

Next in line is the 5.7L (346c.i.) LS1/LS6 aluminum block engine used in the Camaro and Corvette. The limitation on any aluminum block engine is that it cannot be overbored more than 0.010-inch due to the thin iron cylinder liner insert. But with superb fuel control and enhanced lubricants, most often a 0.010-inch overbore will handle most cylinder wall taper issues. These engines also lend themselves to a displacement enhancements to 383c.i. using a 4.00-inch stroke crank.

The next jump in displacement hurtles up to 6.0L (364c.i.) LQ4 and LQ9 truck engines. These engines share the same 3.62-inch stroke as the 5.3L and 5.7L engines, but push the bore out to a full 4.00 inches. This larger bore also improves cylinder head flow by moving the cylinder wall farther away from the valves. The main difference in the two 6.0L truck engines is compression, with the LQ9 having a full half-point more compression at 10:1 versus the LQ4’s 9.5:1 squeeze factor.

Next on the list are the hero engines that seem to get all the attention — like the LS7 427 engine. This is still a Gen III engine, featuring several unique parts, including rectangle port cylinder heads that demand an LS7-specific intake manifold. All previous Gen III engines employed cathedral ports that allowed interchangeability between truck and passenger car engines. The LS7 is distinctive even compared to the other rectangle port heads used on the LS3 or L92 engines.

Beginning in 2005, GM made some minor changes to the LS, creating what has become the Gen IV version. This alteration began with the LS2 engine, a 4.00-inch bore 6.0L aluminum block engine that incorporated some significant changes. The most important change was relocating the crankshaft position sensor from the rear of the block to the front timing chain cover where the camshaft gear included lugs to signal the cam sensor. In addition, to improve ECU accuracy, GM upgraded from the previous Gen III’s 24x trigger wheel to a 58x on the crankshaft wheel.

Following the evolution to Gen IV, GM pushed the displacement ante with the 6.2L (376c.i.) LS3 by enlarging the bore out to 4.065-inch, while retaining the 3.62-inch stroke. Besides increasing the cubic inches, the LS3 also featured the first full production run of rectangle port cylinder heads with massive flow potential that rivaled the old big-block Chevy rectangle port heads from the ’60s and ’70s, both in size and flow potential.

Even that wasn’t enough, and eventually GM rolled out the impressive LS9 6.2L engine with its production 2.3L high-helix supercharger originally installed in the ZR1 Corvette. This dry sump engine cranked out an impressive 638 hp at 6,500 rpm and was quickly followed by Cadillac’s answer with a slightly more conservative LSA wet sump engine making 556 hp at 6,100 rpm. Both engines use a specific forged steel 8-bolt crankshaft that requires its own flywheel/flexplate.

When considering which engine might be best for your next project, one of the first questions must be about displacement. The smallest engines are also the least expensive. But, don’t dismiss them as weak. As mentioned, we recently dyno tested a 140,000-mile 4.8L truck engine. Outfitted with an Edelbrock Performer RPM dual plane intake, 750 cfm Holley carburetor, 1 5/8-inch headers, stock heads, and a mid-sized 219 degrees at 0.050-inch duration COMP Cams hydraulic roller cam, this littlest LS cranked out an impressive 380 hp at 6,800 rpm. We then added mildly ported stock heads and made 430 hp. That’s pretty strong for 293 inches.

The 5.3L might be the best compromise if you are looking to build a mild street car on a budget. We’ve pulled 330 hp and 350 lb-ft of torque from a stock 5.3L engine with only the addition of headers and then added a mild cam of 206 degrees at 0.050. The power jumped to 375 hp at 6,300. While this isn’t earth-shattering in these days of 800 hp street cars, this is excellent power for an everyday driver that would easily push a 3,500 –pound car into the high 12s.

Also high on the list of desirable used engines are the LS3 and L99 variants. These are 6.2L Gen IV engines with rectangle-port head electronic throttles (drive-by-wire or DBW) that can create 430 hp for the LS3. These are aluminum block engines, but don’t expect to find one cheap. We did a quick search of used engines on eBay and the best deal we saw was a take-out L99 6.2L for $4,400. Most of these engines are combined with an automatic trans and wiring harness, and these packages range from $6,500 to $8,500.

Back into a more affordable area are the iron Gen III 6.0L engines from the ’99-’06 era. These are far more affordable. Bone stock, these engines were rated between 300 and 345 hp and up to 380 lb-ft of torque. The most populated of these were the low compression (9.5:1) LQ4, while the LQ9 Escalade versions enjoyed a half-point more compression.

These engines can easily make 425 hp just with the addition of a dual plane intake, 750 cfm carburetor, and headers. Add a mild GM HOT cam and one of these low-compression 6.0L can push out 475 hp.

The reason we really like these engines is that while they are in demand, they are also often overlooked in the hunt for the more impressive aluminum block LS3s. In a recent deal, we scored a 1999 iron-headed 6.0L LQ4 engine for a mere $550. The reason the engine was so cheap is twofold. First, nobody wants an LS with iron heads, especially when combined with the fact the 1990-2000 6.0L engines employed an extended crankshaft flange. This extended flange made it easy for the factory to install the TH-400-based 4L80-E automatic behind this engine using a flat flexplate.

This extended flange can be a hassle if you want to run a manual transmission since it will require a custom flywheel. But if your choice is to run an automatic, even this early engine is a no-brainer. Our plan with this engine is to run small-chamber 5.3L heads to pump up the compression and improve the torque. It will still make 450-plus hp, and with a used intake and carb and new headers, its’ possible to have a 450-hp engine for less than $2,000.

Gen III Engines 

This is a list of the common Gen III and IV engines. This is not a complete list since there will be several iterations of the same engine with minor upgrades or changes.

Gen IV

• These engines feature factory Eaton superchargers

We’ve just scratched the surface of the LS engine family, and the potential these engines offer is amazing. That’s why everybody’s doing it. Sure, you can stick with a small-block or go with a classic big-block Chevy. But for the money, it’s really tough to beat the power and efficiency benefits of a hopped-up LS engine. Why not make that power work for you too!

Sources: Autotronic Controls (MSD), msdignition.com; Champ Oil Pans, Champpans.com; Chevrolet Performance, Chevrolet.com/performance; Edelbrock, edelbrock.com; Holley Performance Products, holley.com; Vortech Engineering, vortechsuperchargers.com; West Coast Racing Cylinder Heads, proheads.com; ZEX Nitrous Systems, zex.com