How popular and effective has the LS engine family become? It is fair to say that the LS engine family is by every measure a worthy successor to the original, now-legendary small block Chevy V8?
As it does, time and technology have marched on, and those advances have allowed the LS to not just equal, but surpass its predecessor. In terms of emissions, fuel mileage and engine longevity, the LS is head and shoulders above the previous Mouse Motor. It might also surprise original small block fans that the LS pumps out considerably more power.
To put this into perspective, the most powerful small block (the fuel injected L84 327) of the muscle car era was rated at 375 hp. Impressive numbers back in the mid-1960s and early 1970s, but the real power output of that small block is about on par with a base-model, 5.3L LM truck motor (the motor that has quietly become the modern small block of choice). Any comparison to the more performance-oriented versions like the LS1, LS2, or LS3 would be pointless—to say nothing of the likes of the 7.0L LS7 or supercharged LS9.
As good as the LS engine family is in stock trim, they wouldn’t hold a candle to the original if they didn’t also respond well to performance upgrades.
Like any internal combustion engine, the LS immediately responds to changes in the big three: heads, cam, and intake upgrades. Boost, of course, is a given!
Though receptive to all three, the change that offers the most bang for the buck with any LS (from the lowly 4.8L LR4 all the way up to the 7.0L LS7) is the camshaft. Nothing wakes up and LS motor like swapping out the stock cam (and valve springs) for a more performance-oriented profile. This is especially true of the milder truck motors (LR4 4.8L, LM7 5.3L and LQ4 6.0L), but even LS2, LS3 and LS7 motors will respond well to a cam swap.
How well you ask?
Check out the supplied dyno results run on the 5.3L LM7 and 6.2L LS3 to see how much power a cam swap is worth, but once you have the right cam, you can then start looking at ported heads and the right intake manifold. Truth be told, you could always just add boost, but that is another story for another day.
Though cam swaps are far and away the most popular upgrade on an LS (for good reason), the early cathedral-port motors will respond to cylinder-head upgrades as well. Power gains are harder to come by on the later rectangular-port motors (L92, LS3 and LS7) because the stock heads already flow enough to support over 650 hp.
Check out the graphs listing the power gains offered by cathedral-port heads on the 6.0L stroker and rectangular-port heads on the LS3. Testing on the LS3 clearly demonstrated that the combination must be plenty powerful before it can take full advantage of the extra airflow offered by ported LS3 heads. Once you have ported heads and the right cam, the final step is to install the proper intake manifold.
Much like the cylinder heads, the cathedral-port combinations will respond much better to something like the Fast LSXR intake (see dyno graph) than the rectangular-port combinations (the stock LS3 intake is already very good).
We have also supplied test data on single and dual-plane, carbureted intakes, and, like the previous generation small block, these intakes are basically rpm specific.
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Other things like displacement, forced induction and even the exhaust system all play a part in power production, but these basics should get you started on your way to understanding LS power production.
Since all of our testing was run on the engine dyno (not the chassis dyno that delivers rear-wheel power), we thought it would be a good idea to provide power numbers on popular stock LS applications for comparison. These power curves were generated by running the motors with no accessories (only an electric water pump), headers (not stock exhaust manifolds) feeding dyno mufflers, and tuned to optimize power production using a stand-alone management system. The motors were also run colder than stock (near 140 degrees). The power curves offered by the four test motors (4.8L LR4, 5.3L LM7, 6.0L LQ4, 6.2L LS3) demonstrate the difference in displacement, cam timing and head flow of the various applications. Not surprisingly, the power curves increased with each hike in displacement, but note that the more aggressive cam timing (LQ4 vs LS3), improved head flow and increased compression ratio combined to greatly improve the power production of the 6.2L LS3 over the similar-sized 6.0L truck motor. (Dyno Chart/Richard Holdener)
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Graph 2 – 5.3L LM7 Cam Test: Stock vs. LS9 vs. 224 Crane
This graph illustrates the amazing power gains offered by swapping a cam on an otherwise stock 5.3L LM7 on the engine dyno. The test involved running the stock motor with the stock 5.3L cam, an LS9 cam (the most powerful factory offering), and a Crane cam offering 0.590 lift, a 224/232 degree duration split and 115 degree LSA. The stock 5.3L heads were set up with a dual valve spring package from Brian Tooley Racing to allow the larger cams. Equipped with the stock 5.3L cam, the fuel injected 5.3L (with headers and no accessories) produced 353 hp at 5,200 rpm and 384 lb.-ft. of torque at 4,300 rpm. After installation of the LS9 cam, the power numbers jumped to 419 hp at 6,200 rpm and 394 lb.-ft. at 5,000 rpm. Note that the 5.3L lost power with the LS9 cam up to 4,500 rpm compared to the LM7, but pulled away rapidly up to 6,500 rpm. The Crane 224 cam pushed thing up even further to 442 hp at 6,200 rpm and 412 lb.-ft. at 5,000 rpm. The Crane bettered the LS9 cam through the entire rev range, but lost out slightly to the LM7 cam below 2,900 rpm. Once equipped with the 224 Crane cam, the motor was in need of ported heads and/or a different intake manifold—like a Fast LSXR. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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Graph 3 – LS3 Cam Test: Stock vs. BTR Stage 3 Cam
Like the 5.3L, the larger (aluminum) LS3 will benefit from the proper cam swap. It bears mentioning that the factory LS3 cam was already much more powerful than the 5.3L cam tested in graph 1, but even so, the BTR Stage 3 cam (and springs) increased the power output of the otherwise stock LS3 crate motor from 496 hp at 5,900 rpm and 491 lb.-ft. of torque at 4,700 rpm to 570 hp at 6,500 rpm and 522 lb.-ft. of torque at 5,300 rpm. The BTR camshaft increased the power output through the entire rev range—no easy task with a stock cam at the lower rev ranges. The reason for the increased power at lower engine speeds is that the stock LS3 cam was not terribly effective at lower engine speeds (at least not compared to a milder LM7 cam), so it is easier for an aftermarket cam to add power down low compared to the LS3 cam. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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Graph 4 – Head Test: LS1 vs. TFS Gen X 235 (408 Stroker)
Cylinder head upgrades on a cathedral-port application can make some serious power as indicated by this test on a 408 stroker. This test involved a comparison between the stock LS1 heads (with a valve spring upgrade) and a set of CNC-ported, GenX 235 cylinder heads from Trick Flow. The test motor was a 408 stroker produced by the installation of a 4.0 inch SCAT stroker crank, rods, and JE Pistons into an iron 6.0L block (bored .030 over). The test was run with a Fast LSXR intake and 102mm throttle body, and long-tube headers. Naturally the 408 was also equipped with a healthy cam, in this case a Crane that offered 600 lift, a 240/248 duration split and 114 degree LSA. Equipped with the stock LS1 heads, the 408 stroker produced 549 hp at 6,200 rpm and 517 lb.-ft. of torque at 4,800 rpm. After installation of the TFS 235 heads, the power jumped to 601 hp at 6,300 rpm and 546 hp at 4,800 rpm. The head swap was worth over 50 horsepower, but remember, the power gains will be a function of the output (airflow needs) of the test motor. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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Graph 5 – Head Test: LS3 vs GM CNC L92 (LS3 Crate Motor)
This test illustrates what happens when you add ported cylinder heads to a motor that already has sufficient head flow. The stock GM LS3 crate motor from Gandrud Chevrolet was basically a Corvette LS3 pulled from the assembly line. The LS3 was factory equipped with rectangular port, LS3 heads that flowed near 315 cfm, or enough to support well over 600 hp. This motor was rated by GM at 430 hp, but run in our configuration on the engine dyno (headers, no accessories and tuned to perfection), produced 495 hp and 484 lb.-ft. of torque. After adding the CNC-ported L92 (automatic-equipped Camaro LS3) heads that flowed 350 cfm, the power output jumped by just 7 hp (to 502 hp). This doesn’t mean the ported heads don’t work, it is just that this mild test motor could not take advantage of the extra 35 cfm offered by the ported heads. Run on a wilder 468 inch stroker application, the ported heads were worth closer to 30 horsepower. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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Graph 6 – EFI Intake Test: LS1 vs. Fast LSXR (Modified 6.0L)
Truth be told, the stock LS1 intake was one of the low men on the factory intake totem pole, only bettering the LS4 intake. The early truck, Trail Blazer SS, and LS6 intakes all offer improved power over the LS1 intake, with the Trail Blazer offering the best power gains of the bunch. This test involved a comparison between the LS1 and a Fast LSXR (102mm) intake and throttle body on a modified 6.0L. The 6.0L featured forged internals from CP and Carrillo along with a healthy Comp 469 Cam (0.617/0.624 lift, 231/247 duration, and 113 LSA) and AFR LSX 230 V2 heads. Run with the LS1 intake, the 6.0L produced 535 hp at 6,900 rpm and 468 lb.-ft. of torque at 5,100 rpm. After installation of the Fast LSXR intake and 102mm throttle body, the power jumped to 590 hp at 6,800 rpm and 505 lb.-ft. of torque at 5,600 rpm. The right intake for the combination is critical for power production. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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Graph 7 – Carbureted Intake Test: Edelbrock Performer RPM vs Victor Jr. (Modified 6.0L)
This test was run on the same modified 6.0L test motor as graph 4 (AFR LSX 230 V2 heads, Comp cam, and forged internals), but this test involved carburetion. This test demonstrated the quintessential single vs dual-plane intake power curves. Dual-plane intakes were designed to provide a broad torque curve, while single-plane manifolds focus power production higher in the rev range. The dual-plane suffers slightly at the top of the rev range compared to the single plane, but the opposite is true at lower engine speeds. The dual-plane generally offers much more torque and that is exactly what this test showed. Run with the dual-plane Performer RPM, the modified 6.0L produced 544 hp at 6,900 rpm and 470 lb.-ft. of torque at 4,300 rpm. The single-plane Victor Jr. countered with 552 hp at 7,000 rpm and 463 lb.-ft. at 5,200 rpm. Note the substantial torque gains offered by the Performer RPM below 4,800 rpm, but the Victor Jr. only bettered the RPM by a handful of horsepower at the top. The choice comes down to where you want your power production. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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Graph 8 – Stock vs. TFS Heads, Comp Cam & Fast LSXR Intake (5.3L)
It is amazing what kind of power gains are available from upgrading the heads, cam and intake. Using the stock 5.3L short block, we added a set of TFS Gen X 205 heads, a Comp 281LRR cam (0.617/0.624 lift split, 231/239 degree duration split at .050, and 113 degree LSA), and Fast LSXR intake and throttle body. Run in stock trim with headers, no accessories and tuned with a Holley HP management system, the stock 5.3L produced 353 hp at 5,200 rpm and 384 lb.-ft. of torque at 4,300 rpm. After swapping over the new heads, cam and intake, the power numbers jumped to 503 hp at 6,600 rpm and 443 lb.-ft. of torque at 5,600 rpm. That represented a gain of over 150 hp peak to peak and the gains were even more significant (nearly 200 hp) higher in the rev range. Wilder cams (to the limit of piston-to-valve clearance), a short runner intake, and even better heads netted 550 hp on an aluminum L33. (Dyno Chart/Richard Holdener)(Image/Richard Holdener)
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The LS engine family is powerful in stock form but really comes alive when you add the right performance components. (Image/Richard Holdener)The number one modification for any LS motor is a cam swap. Since the stock motors already have sufficient displacement, head and intake flow (especially the LS3), all they need is a more aggressive cam profile. (Image/Richard Holdener)After a cam swap, you should start looking at the head flow, especially on a cathedral-port application. Since the rectangular-port, LS3 and LS7 heads already flow enough to support 650 hp, ported heads offer smaller power gains on all but wild stroker applications. (Image/Richard Holdener)Cathedral-port applications respond well to intake upgrades like this 102mm Fast LSXR manifold, but the factory LS3 intake is pretty impressive. Unlike the LS3, there is considerable power waiting to be unleashed by swapping out the factory LS7 manifold. (Image/Richard Holdener)Combine the right heads, cam and intake and you can create on serious LS motor, even when using the stock short block. (Image/Richard Holdener)
Richard Holdener is a technical editor with over 25 years of hands-on experience in the automotive industry. He's authored several books on performance engine building and written numerous articles for publications like Hot Rod, Car Craft, Super Chevy, Power & Performance, GM High Tech, and many others.
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