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INTRODUCTION

Even the competition has to agree that Chevy’s LS engine family is more than just a worthy successor to the original small-block; it’s one hell of an engine. The Blue Oval boys were jumping up and down about their new 5.0 Coyote, but (as usual) they were still behind the eight ball in terms of displacement and power output. Although the new four-valve 5.0 modular engine offered reasonable high-RPM power, it was decidedly lacking in low-speed power compared to the LS3. Credit the extra displacement offered by 6.2 liters of displacement (7.0 liters on the LS7) for all that wonderful torque.

High-RPM power is all well and good, but the vast majority of spirited (street) driving comes lower in the rev range. Besides, in the LS (3 or 7) there is no choice between low-speed and high-RPM power, as the GM engines offer both. Toss in the fact that the LS3 and LS7 featured lightweight, all-aluminum construction, composite intakes, and even variable cam timing, and you have a traditional small-block with all the technology of a DOHC Ford engine, without the penalties in size, weight, and complexity.

In the original muscle car era, it took a big-block to muster power ratings that exceeded 400 hp and a like amount of torque, and those old power ratings were gross and not net! The LS3 and LS7 made this a good time to be a Chevy owner, but this book is all about how to make a good thing even better.

The LS engine family has evolved constantly to keep General Motors ahead of the competition. The original LS1 was a solid step above the LT-1, just as the LT-1 easily eclipsed the performance of the previous L98 TPI engine. The LS3 followed the 5.7 LS1/LS6 and 6.0 LS2 performance engine configurations.

Starting with an increase in displacement, the LS3 checked in at 6.2 liters versus the previous 6.0-liter LS2 combination. This came courtesy of an increase in bore from 4.00 inches (in the LS2) to 4.065 inches (the two shared the same stroke of 3.622 inches). The increase in bore size increased displacement and airflow because head flow increases with bore size. The LS7 took this one step further by combining a 4.125-inch bore with a 4.0-inch stroke.

The revised cylinder head(s) that replaced the cathedral-port design with a more conventional rectangular port helped make the LS3 and LS7 serious small-blocks. Tested on the flow bench, production LS3 heads flow as much as 315 cfm right out of the box (350 cfm for the LS7 heads). Those are flow numbers reserved for race heads not long ago, and it takes pretty serious 23-degree small-block (or even cathedral-port LS) heads to reach the flow numbers offered by the stock LS3. Despite flow figures that suggest supporting more than 630 hp (I made as much as 690 hp with a set of stock LS3 heads on a 468 stroker), additional flow is available with proper porting or the substitution of aftermarket LS3- or LS7-based cylinder heads.

Stock LS3 and LS7 heads offer massive airflow, and it’s one of the major reasons that they respond so well to cam swaps. A cam is really the only thing missing in the LS package (along with valvesprings). One important point to mention regarding testing in this book is that because the stock LS3 and LS7 cylinders heads offer so much flow, you shouldn’t expect huge power gains from a head swap, no matter what the flow bench says. If your modified LS3 (or LS7) makes 600 hp with a set of (350 cfm) heads capable of supporting 700 hp, don’t expect much of a change when you add heads with (400 cfm) flow numbers that support 800 hp. The problem isn’t (likely) the ported heads, but rather the engine. See Chapter 4 to find out how much power ported heads are worth on combinations ranging from a stock LS3 to a 495-inch stroker LS7.

In addition to camshafts and cylinder heads, this book contains separate chapters on nearly every aspect of LS3 and LS7 performance, including intake manifolds (Chapter 1), nitrous oxide (Chapter 7), and even forced induction (Chapters 5 and 6).

Chapter 5 covers all the forms of supercharging, including Roots, twin-screw, and centrifugal superchargers. Chapter 6 on turbocharging covers both single and twin turbo testing. As well as LS3 and LS7 engines respond to camshafts, they respond even better to boost. Using boost from a supercharger or turbocharger, it is possible to increase the power output of your LS3 or LS7 by 50 to 100 percent or more. As illustrated by the test data in the two chapters, boost is simply a multiplier of the original output. Adding a turbo or supercharger to a stock engine results in less of a power gain at any given boost level than adding the same boost to a modified engine. I also cover the results of turbocharged and supercharged cam testing because the specs differ on cams designed for forced induction.

One thing you will find out about the LS3 and LS7 in this book is the relative strength of their intake manifolds. Testing has shown that the factory LS3 intake is very tough to improve upon. It is possible to increase power higher in the rev range (usually beyond 6,500 rpm) with a short-runner intake, but this usually comes with a trade-off in power lower in the rev range. The two tests on the adjustable intake manifolds (mine and the unit from FAST) clearly illustrate this effect on the power curve.

The comparison between single- and dual-plane carbureted intakes shows this as well, as intake manifolds are designed to operate effectively at specific engine speeds. Short-runner (or single-plane carbureted) intakes should be combined with more aggressive cam timing designed to enhance power production higher in the rev range. By contrast, the factory LS7 intake is very limiting, with significant gains available from an upgrade. Working with intake manifolds are throttle bodies, which offer increased flow. The gains offered by throttle body upgrades increase with the power output of the engine. Tested on a stock engine, a throttle body upgrade might be worth nothing, but tested on an 800-hp combination, it can be worth as much as 50 to 60 hp (especially on a positive displacement supercharged application).

Chapter 7 discusses how nitrous oxide can be applied to any LS combination, ranging from a stock crate engine to a dedicated stroker (including turbo and supercharged combos). The amount of power supplied by nitrous oxide is a function of the jetting, as larger jets allow more nitrous flow. Of course, this must be accompanied by the proper amount of fuel, but nitrous systems offer far and away the most bang for the buck. It is possible to add as much as 250 hp (or more) to your LS for about the cost of a cam swap. Although you make more power with nitrous and a cam, every LS owner should experience nitrous oxide once in their life. I have divided the chapter into individual components (i.e., heads, cams, and intakes), but the reality is that the best way to produce optimum power from your LS3 or LS7 combination is with the proper combination of components. The heads must work with the cam timing and intake design to optimize power production in the same RPM range.

Chapter 8 illustrates the testing of combinations designed to work together, ranging from the stock LS3 crate engine to a massive RHS stroker displacing nearly 500 ci.

If you want to know how to make your LS3 or LS7 more powerful with dyno-verified results, you’ll find it in these pages.