LS/LT Encyclopedia: Modern GM Small-Block V-8s, Part 1
Welcome to a brief series that charts the evolution and features of the modern GM small-block. We begin with a quick backstory and then hop into the details of the most ubiquitous V-8 engine family of the 21st century. Stay tuned for parts two and three. —Ed
Preamble: The Road to LS
In 1955, Chevrolet chief engineer Ed Cole introduced the world to the small-block Chevy V-8. His revolutionary design was the perfect recipe to satisfy a domestic market ravenous for attainable speed. The small-block “mouse motor” was lighter and more compact than any of GM’s previous work in the field of bent eights, not to mention that of its unsuspecting contemporaries from across town or the six-bangers it replaced in Bow-Tie showrooms. This condensed V-8 cemented its status with big power and even bigger potential in the aftermarket.
For nearly two decades, The General continued to perfect Cole’s blueprint, extracting more and more power through the introduction of fuel injection and higher compression ratios. Weight was cut through the use of new materials and manufacturing processes. Even after the day the horsepower died, Cole’s masterpiece would soldier on into the malaise era of the late ‘70s and early ‘80s as a faintly shining beacon, reminding gearheads of the good days while offering as much oomph as it could legally get away with.
Father(s) of the LS: The DOHC LT5 and the Short-lived Gen II Stepping Stone
By the mid-’80s, General Motors was ready to spark an American performance comeback by minting a powerplant that could live up to the acclaimed handling of its hot new C4 Corvette. Coincidentally, GM had a controlling interest in Lotus at the time, so, naturally, the famed sports car maker and seven-time F1 Constructor’s champion was tapped to take the lead on the “King of the Hill” project. The LT5 V-8 that materialized from this partnership shared its 5.7-liter displacement and trademark 4.4-inch bore spacing but not much else with its lesser siblings. It brought dual-overhead cams to America’s Sports Car for the first time. Its four valves per cylinder were joined by 16 fuel injectors and a bottom end built from an aluminum block with a forged steel crank and connecting rods that netted an 11.0:1 compression ratio. Its state-of-the-art construction brought a third partner, Mercury Marine, into the fold to handle assembly. From the time the C4 ZR-1 that housed this masterclass in modern combustion hit the market in 1990 through 1992, the LT5 made 375 raucous horsepower vs. the 245 of the L98 in the base ‘Vette and, for context, the 225 of the “5.0” in the most powerful Mustang on the market; it was a monster!
The ZR-1’s uncanny ability to sustain 175 MPH immediately became the stuff of legend, and as Lingenfelter would later prove, the LT5 still had a lot of room to grow. However, the high expense of its production and the public’s waning interest in buying ZR-1s forced GM into a difficult crossroads with far-reaching implications. With an improved 405-horse LT5 set to bow in 1993 and the possibility of a 475 or even 500 HP variant within reach, Option A involved staying the course and further developing the 32-valve motor that already had significant time, money, and effort sunk into it. Option B? Pulling the plug with a drastic cost-cutting righthand turn, taking everything learned from the pricey ZR-1 detour and applying it to its birthright by vastly improving the timeless pushrod V-8.
The offramp was taken, the band-aid was ripped off, and the first Gen-II small-block was born. It was dubbed LT1 as an homage to the Mighty Mouse’s 1970 highwater mark. The new LT1 used a new block, intake manifold, and cylinder heads along with a “reverse cooling” system, but the basic design, including engine mounts, bolt patterns, bore spacing, and the 5.7L displacement of its direct predecessors, carried over for maximum parts sharing between generations.
This revamped LT1 hit base Corvette engine bays in 1992 with an even 300 ponies and 330 lb-ft of twist, delivering once again on the premise of affordable performance by offering 90 percent of its high-tech big bro’s performance at a 50 percent discount and almost instantly pushing the mighty ZR-1 into the background of public consciousness.
With GM’s final obligation to the LT5 complete and one model year remaining before the changeover to the long-awaited C5 Corvette, the stopgap Gen-II small-block earned itself a swansong upgrade for 1996. Meant as the mechanical highlight for the one-year homage to the fabled Grand Sport racers of the ‘60s—but featured in every manual transmission 1996 ‘Vette—the LT1 was worked over with a lightweight valvetrain and strengthened crank, resulting in a 30-horse bump and a unique “LT4” designation to take the Chevy small-block’s fleeting but significant second iteration into the sunset in style.
LS Rises: The Complete Guide to Gen-III Performance Small-Blocks
Engine: LS1
Displacement: 5.7L
Max Power/Torque: 350/365
Model Years: 1997-2004
Domestic Applications: C5 Corvette, Fourth-Gen Camaro/Firebird (1998-2002), 2004 Pontiac GTO
The Gen-III “LS” small-block made its debut in 1997 in where else but under the long, low (a characteristic feature permitted by GM’s re-commitment to pushrods earlier in the decade!), sculpted hood of the C5 Corvette. Its first representative, aptly dubbed “LS1,” still displaced 5.7 liters, but other than the familiar displacement, its characteristic 4.40-inch bore spacing, and its rod bearings, it represented a clean-sheet effort with flexibility at the core of its mission. As opposed to the LT1’s 4.00-inch cylinder bores and 3.48-inch stroke, the LS1 reached 5.7 liters through a 3.899 x 3.622 bore and stroke. From the word “go,” the third-gen small block was intended for use in cars and trucks, could be manufactured in either aluminum (cars—our focus, here) or cast iron (trucks), and able to take on multiple displacements. It quickly earned a reputation for durability, remarkable power production, and surprising efficiency while remaining easy and affordable for GM to manufacture and for dealers, tuners, and individuals to service, upgrade, and, of course, swap.
Engine: LS6
Displacement: 5.7L
Max Power/Torque: 405/400
Model Years: 2001-2005
Domestic Applications: C5 Corvette Z06, 2004-2005 Cadillac CTS-V
The hi-po version of the LS1 arrived along with the first modern Corvette Z06 in 2001. It also received nomenclature from the golden age of American muscle, earning the LS6 classification last used on 454 big-block Chevelles and Corvettes of the early ‘70s. The LS6 soldiered on at 5.7L but was fortified with improved main web strength, a higher-lift cam, greater compression (10.5:1), a revised oiling system, and more, including the first mass-market use of a titanium exhaust system following the lead of the McLaren F1. It debuted with 385 horses but proved GM’s bet on pushrods wise by equaling the LT5’s 405-horse output for a fraction of the cost in 2002. The LS6’s unique intake manifolds were also used on all 2001 and later LS1s, gifting the Corvette LS1 a five-pony boost from 345 to its final 350-horse form. When Cadillac was reborn in the sporting image of BMW a couple of years later, the first member of its M-fighting V-Series brought the strongest powerplant available—an LS6 with a five-HP Corvette tax imposed—together with the new-for-2004 Art and Science CTS sedan.
A good start. Looking forward to the rest. I still love the ZR-1’s LT5 and would have wanted to have seen a next generation model.
Please finish the story. I have had 2 Corvettes and now a 2023 Camaro SS V8. Quite curious I am.
From the non-Corvette perspective, I know of three variants of the SBC which largely involve the heads. There’s the early ones everyone is familiar with, there’s a version where they revised the intake bolting at the exhaust crossover so those four bolts went in straight down instead of on an angle. These also have the valve covers bolting straight down the middle instead of around the sides. These are generally TBI engines but a few truck variants and marine engines took the Quadrajet. Then there was the SBC block with Vortec heads which might have been around for a year or so. I sold one of these to a buddy and had to go around a few times explaining yes it’s a Vortec but it is not an LS… a lot of folks use those two terms interchangeably.
I don’t consider an LS or any of the similar variants to be a ‘small block’. SBC was a very specific family of engines that died in the 90s
I agree.
They are all small-block Chevrolet engines. The earlier ones were the first generation (and I have owned 4 of them), but that does not give them exclusive rights to use the SBC name.
The LT5 was a very expensive and complex engine. Therecwas not much future as a Corvette engine with dropping C4 sales.
The LT1 was about advanced as the original based engine was going to go. The Vette team snd Chevy wanted a more efficient yet powerful engine that would meet the new emissions and CAFE.
So other than bore spacing everything is new. This made a more compact, stronger lighter engine. This was key to the new C5 they brought back ftom the dead. Even the head of Jaguar stated he was envious of this engine and how low it was in the car.
The LS was and still is an amazing engine.
John Lingenfelter did so much more with the LS vs LT5. The addition of twin Turbochargers he was making street C5 corvettes able to top 230 mph. He stated they could make even more power to hit 300 mph. I asked him if he was going to do that. He said not. It could be done but with no cage in the car there would be little left if a tire failed.
Even with more power to come the non supercharged GS C6 is said to be the Corvette teams favorite car for track use in the Coupe. It has all the track coolers and dry dump. Steel frame and enough power to make it easier to drive as the SC car could be difficult.
The real treat is the LSX engine block that can be used for even greater things.
I believe you meant to say aluminum chassis on the C6 Z06. That seems to be the engine you are describing with the dry sump and coolers.
He was describing the Grand Sport
All I know is that we have an LS3 stroker in our (Ford) endurance racer and it makes me smile every time I stand on the throttle. Dynoed at 527 crank HP with a big Holley double pumper. 155 mph on the front straight on the Daytona road course.
I have a 66 Mustang fastback almost ready for the motor and I would love to drive it at Waterford Hills track.
I keep saying LS3, LS3!!!!
The Mustang is a Ford, and should have a Ford engine. How about a 1968 427 Ford engine?
What about ls7
I have both the LT-1 engine (1970 Corvette) and the LS 6 engine (2003 Z06). I love them both. The Z06 gets driven a lot more because of it’s handling.
Does anyone out there know what the true horsepower figure for the 1996 LT-4 was/is? I have heard many stories of higher horsepower backed by zero factual evidence. Very reminiscent of the 1967-1969 Z-28 290 hp rating. I owned a 1969 Z-28 and 290 seemed a tad conservative, but I had no benchmark having gone from a 1967 VW Beetle to the Z-28. The Camaro immediately impressed me as a car requiring some caution while operating it. 🙂
The real advancement was substitution of pressed sheet steel rocker arms for the cast steel versions used theretofore. Not just cheaper but much lighter…that meant the engine could rev effortlessly…equals performance!
Having owned 4 of the original generation small-blocks, as well as an LS1 (2002 Camaro) and an LS4 (2009 Buick Lacrosse Super), I guess I must like them all.
I have lost count of how many small blocks I have owned and built. I was worried of the new LS type so when I went shopping for a Trans Am in the late 1990s, I wind up with a 97 with the LT one good motor a bit troublesome cooling system.(reverse flow, if overheated one must allowed to cool completely and purge it). most recent engine R&R was on our 68 Camaro convertible. I swapped in a 70s marine engine equipped with 993 heads a marine cam Edelbrock C3 BX manifold and I’m running an 1850 carb. The original 350 is out for rebuild; forged crank,camel hump heads,10.25:1 compression. plan as a competition cams dual pattern flat tappet. I also brought Don the machinist the 73 Camaro motor for parts, etc.. the original motor is a restoration rebuild;the 73 motors going to be short blocked and I’ll put aluminum heads and maybe a roller cam we’ll see. I have three vehicles with LS series motors in them never had to build one. They’re too damn good! The pick up is a 6 L iron block aluminum head. It has 211 K. my C5 is the 2001 with the revised intake manifold. I have about 39,000 miles on that one. The driver is a 2021 Tahoe with a 5.3 aluminum motor 54K and counting runs great gets 18 miles per gallon at 100 miles an hour.(interstate 80 Nevada.) oops forgot one: 2022 ZL1 Camaro with the LT 4-Nuff said.PS a small block and an LS are two different motors IMHO.PPS even the Ford guys are using these motors, I read it here. My neighbor has a 50s Teebird with a small block in it! he’s even running the magnificent Muncie transmission…
I see LT1, LS6, LT4, LS, LT5 and on and on. Does anyone have a clue as to how these nomenclatures came about or in fact do they mean anything specifically. I have searched and searched for an answer and no one seems to know. Here’s another, Z06, what??????
At one time those alpha- numeric designations were known as Regular Production Options (RPO) codes. “L” seemed to be reserved for engines. I wonder if anyone really knows how the RPOs were derived.
In in 1969 I ordered and still have a Z/28 302. Back then they built the ZL1 aluminum block and head 427. I wish I would have known about them, I would have had one. Recently, I don’t know the year GM built a 6.4 L (I think)blown engine called ZL1 then later they built Z28 with 427 in them. Now I hear they’re building 2025 Z28 with a 5.5 l engine. So far I’ve had 283s 327s 302s 305s 307s 350s 400s 1-366 1-396s 427s 454s and 1-4.8L and 2-5.3L’s!! I, like you, am confused, and would like to learn also!