Feature: Gen III Motors - What’s the Deal?

Story by Tim Baillie

It takes serious guts to replace the most famous engine of all time. Since 1955, GM had been building its Chevrolet Small Block V8 with accolades, respect and awards in the automotive press and racing and with commercial success with customers in marine, industrial and mainstream automotive markets. The Small Block was the most purchased, modified and swapped engine of all time.

The introduction of the Gen. III motor in 1997 was actually understated, and it may have been this was so as to not lose the loyal followers of the original Small Block. It was not until these motors got into the hands of enthusiasts that they began to realize the importance of what GM had done:

• deeper engine skirt for increased engine rigidity and a decrease in distortion for less noise, friction, wear
• six-bolt main bearing caps in lieu of two- and four-bolt caps
• head design increases volumetric efficiency, therefore more power at all engine speeds
• quieter and more efficient valve train operation
• new firing order for smoother idle and less vibration throughout the operational range
• elimination of Exhaust Gas Recirculation (most engines) by achieving a more complete burn the first time
• coil-near-cylinder design; shorter plug wires for a double-hot spark
• one coil per spark plug; individual cylinder timing can be tuned on the fly via the PCM and knock sensing
• powerful and reliable power train control computer with the ability to holistically control more engine (and automatic transmission) processes than ever
• throttle-by wire (most models)
• same overall size as the original Small Block, offering tremendous power output for such a compact size envelope
• 400,000-mile longevity design

When the LS1 arrived in 1997, it was the motor to have for Hot Rodders just as the LT1 was before that and the TPI before that. These motors were popular mostly because they were the powerplants of GM’s top car, the Corvette. The LS1 was in high demand and that demand called for a high price tag from Auto Recyclers who had them in their inventory. When the LS2 came out, it replaced the LS1 and now, most recently, it has been replaced by the LS3. The higher-performance LS6 was replaced by the LS7 and then came the Supercharged LS9.

The one thing that most people didn’t know, didn’t realize or didn’t care about was that while all these high-performance LS motors were being released, the same motor design was being used in every V8 truck since 1999. Most people didn’t realize that under that traditional “Vortec” engine cover was the same Gen III-design motor as the Corvette and Camaro, not the older well-known “Vortec” motor of the ‘90s.

In 1999, GM’s LS1 was 5.7-litre (346 cu-in), 3.90-bore block motor which put out 305 hp in the Camaro and 350 hp in the Corvette. Now at the same time in 1999, GM released the LM7 / L59 5.3 Gen III motor into its truck. It was a 5.3-litre (325 cu-in) 3.76-bore block motor putting out 285-320hp (model depending).

In 2005, GM released the LS2 6.0-litre (364 cu-in) 4.0-bore block motor which was putting out 400 hp in the Corvette and GTO. The trucks had been using a 6.0-litre (363 cu-in) 325-hp LQ4 motor since 1999 and then the H/O 6.0-litre 345-hp LQ9 in 2002.

Now, the price difference between an LS2 and a LQ4 or LQ9 is drastically different. While an LS2 (complete with harness, ECU and throttle pedal) was and still is going for $5,000+, the LQ4 and LQ9 are well under $2,000.

Now that we have laid out a basic comparison between the famed LS Gen III motors and the Gen III truck motors, we can really get to the point of this article.

In the last few years, people have come to realize that while it’s nice to say “I have an LS2 under my hood,” the reality is that not everyone can afford to buy an LS2, but they can afford a Gen III truck motor and get the same power if not more power for less than half the price. That’s right, less than half the price of an LS2.

The main architecture of the Gen III and the newer Gen IV motor is the same; for the most part, they use the same block, same head design and almost all of the parts are interchangeable from intakes, heads, and front drive assemblies to little things like rockers, valves and throttle bodies. You can take a 5.3 LM7 truck motor, put LS1 heads on it with a LS2 intake and throttle body along with a front drive assembly from a Corvette, Camaro, GTO or a Truck on it and it will all work together. All you need is to make sure you have the correct ECU and throttle body (if using a cable driven TB) or have the correct ECU, Throttle Body, Throttle Pedal and TAC module to make it all work, and all of those parts can be interchanged.
Confused yet? Well it is confusing, but in reality it isn’t if you have the right information. This chart gives you the basic rundown of all of the Gen III and IV truck motors with their RPO engine name.

Next issue, we will go into detail as to what all this means and what kind of unlimited options there are out there for Gen III motors.

If you have any questions about installing Gen III motors into your car or what’s needed to make a truck motor work for you, please contact us.

Tim Baillie is owner of HzEmall Customs in Surrey B.C. and serves as Project Manager for this publication. You can reach Tim at 604-888-6568 or tim@rpmmediaprojects.com

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