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The LS Turns 20 … and Retires

HOT ROD logo HOT ROD 9/25/2017 Hot Rod Network Staff
03-ls-20-year-anniversary The LS Turns 20 … and Retires

It's enough to give the rest of the V-8 world an inferiority complex. Big, V-8 engines are very much an American thing while the rest of the world seems to prefer buzzy little four cylinders or perhaps quiescent electric motors. But here in the land of the free and home of More Torque, our preferences lie with big, powerful two-valve pushrod engines.

Perhaps it's appropriate that the movie The Lost World, Jurassic Park opened in 1997, the same year as the LS1. Appropriate because this latest iteration of the small-block Chevy really made the Gen I small-block seem antediluvian. In a quick two decades, even that original LS1 now seems frail compared to today's steroidal Gen V technology.

We thought it might be fun to look back at how far this all-aluminum small-block has progressed, make some comparisons, and track its progression from the humble LS1 to the assertive Gen V LT1 and big-brother LT4.

Legacy is an appropriate descriptor that's often applied to the Gen III family of engines that grew out of the Gen I small-block of 1955. The LS1 retained several important design aspects, including the small-block's 4.400-inch bore spacing as well as the same bellhousing bolt pattern. This nod to the past was no accident. These simple steps allowed car builders to easily adapt the new LS to older cars, creating a whole new segment of the performance industry.

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While the Gen III is architecturally more similar than different compared to its Eisenhower-era predecessor with pushrods, two valves per cylinder, and a wedge combustion chamber, that's pretty much where the similarities end. Besides the deep-skirted block that adds strength, the most significant changes were all in the cylinder heads. Port flow increased dramatically, accompanied by a radical shift from a 23-degree valve angle to a much flatter and flow-enhancing 15-degree angle accompanied by attendant changes in the ports that complemented the valve angle. Plus, a far flatter and more efficient combustion chamber allowed a welcomed increase in compression. The changes not only added power but were accompanied by improved fuel economy and lower exhaust emissions. This was the engineering equivalent of a trifecta.

Taking a somewhat broader view, improving power and efficiency can only be achieved with control. If we look at the Gen III, it is a study in controlling events. The engine control Unit (ECU) knows not only where the crank is at all times but the camshaft as well and can manipulate performance and mileage with injector pulse width, electronic throttle control (ETC), and timing.

The ECU knows when the engine detonates and can adjust for that on the fly, compensating for elevated engine inlet air temperature, all while making tuning adjustments in millisecond increments. Even the smallest of the Gen III engines, the 4.8L and 5.3L truck engines, enjoyed major power improvements over the Gen I and II designs.

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The first big performance enhancement came with the LS6 bumping power by 55 hp to 405. It was clear a horsepower race was enjoined with the appearance of the 427ci, 7.0L LS7 touting 505 hp and 470 lb-ft of torque. Everybody wanted an LS7. It reminded the older guys of the rock 'n' roll '60s, right down to the RPO numbers. But what was this? A factory V-8 with a dry-sump oiling system? Only race cars have dry sumps. The sprint was now a full-on stampede. What could they do to top an LS7?

The LS2 actually predated the LS7 and quickly experienced a few minor improvements that were sufficient to call it a Gen IV engine. This engine enjoyed a displacement bump to 6.0 liters with a 4.00-inch bore and base power of 400 hp, but that remained only for a short time until the LS3 debuted. Here was where the promise of big power began its climb.

Engine guys could see the telltale signs with the single Internet digital image of those rectangle-shaped intake ports. Those ports where huge, everyone said. And the power numbers jumped again along with displacement now up to 6.2 liters (375 inches). Could it get any better? Absolutely!

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The horsepower escalator was hooked directly to GM's dyno cell and those guys in the white coats were pushing all the right power buttons. You can only get so much from using atmospheric pressure, so the next best thing was to use a pump to push the air into the intake ports. The LS9 was essentially the answer to the age-old quest. The C6 Corvette raised the stakes with 638 hp and 604 lb-ft of torque using a Roots-style Eaton 2300cc supercharger on top of an already outstanding 6.2L engine. This made monster power and carried a warranty!

This was followed by a milder LSA supercharged version for the ZL1 Camaro and Cadillac CTS-V, this time with a smaller 1.9L Eaton blower making 556 hp and 551 lb-ft of torque. Both the LS9 and LSA are now available as crate engines in Chevrolet Performance's expansive 400-page horsepower catalog with the LSA the much more affordable of the two. Keep in mind as well that these are SAE horsepower and torque ratings that are much more conservative than the typical hot rod correction factor. The difference is the factory rating system is about 5 percent lower than the hot rod factor, meaning that a 556 hp rating for the LSA is roughly equal to 580 hp using the hot rod correction factor. This is true for normally aspirated engines as well.

While power is always a good thing, control has improved at the same time. Fuel mileage has often thought to be the antithesis of performance, but creative engineering means coming up with ways to accomplish both. First it was variable valve timing (VVT), which exerts control over cam timing by allowing the ECU to advance or retard the cam as much as 62 degrees in Gen IV engines. Add to that what GM calls Active Fuel Management (AFM), which really is the art of pulling four cylinders off line under light power applications in search of better fuel mileage.

The search for more internal combustion power throughout the 20th century was most often accomplished on either side of the combustion chamber. But to the true devotees of combustion science, much of the real magic happens in the combustion space above the piston. The Gen IV engines had proved to be excellent role models with regard to power, which of course predicated a goal toward increased efficiency. The next step toward increased fuel management was to move its point of entry from upstream of the intake valve to inside the combustion chamber. The acronym creators call this gasoline direct injection or GDI.

This is not new science. Diesel engines have been perfecting this art for nearly as long as the internal combustion engine. Sprint Car engine builders have been doing this for decades. The key to GDI was to improve the combustion event with the goal of extracting more power from less fuel. The trick to injecting fuel into the combustion chamber is to do so at extreme pressures to ensure vaporization. This is exactly what the Gen V LT1 is all about. A high-pressure pump located just above the lifter valley generates pressures as high as 2,300 psi. The mechanical pump is driven off the camshaft and the fuel is shot directly into the center of the combustion space on top of the piston just after the intake valve closes.

Not only does this precisely control the fuel to each cylinder but the direct injection also allows a higher compression ratio for the same octane, which has the mutually beneficial effect of improving fuel mileage while simultaneously increasing power. While the LT1 has garnered much of the attention as the engine for the Corvette and Camaro, GDI is also shared with the newest truck engines as well. The 5.3L L83 and the 6.2L L86 truck powerplants are not only all-aluminum torque beasts but also enjoy the benefits of GDI.

A little-known fact about the L86 truck engine is that while its horsepower rating is down compared to the LT1, by merely installing the LT1 oil pan and intake manifold on this engine, you essentially have an LT1 as all other aspects, including the compression ratio, cylinder heads, and the camshaft as they are all the same. GM merely tuned the intake manifold to build more torque for the truck applications. So in the near future, it would pay dividends to keep an eye out for the L86 as another of the best deals in horsepower to come out of the small-block legacy.

So while the Gen III LS1 is now 20 years old and has been usurped by its newer Gen V cousins, the foundation of pushrod, two-valve-per-cylinder performance is still as robust as ever. Let the other guys build their ultra-complex, dual overhead cam engines. The line still forms just behind the Gen V. It would be smart to check in with the LS movement every once in a while. It's bound to change again soon and no doubt for the better.

Power Numbers

EngineDispl.HPTQ
LS1, Gen III5.7L, 346ci350365
LS6, Gen III5.7L, 346ci405400
LS7, Gen III7.0L, 427ci505470
LS2, Gen IV6.0L, 364ci400
LS3, Gen IV6.2L, 376ci430425
LS9, Gen IV*6.2L, 376ci638604
LSA, Gen IV*6.2L, 376ci556551
LT1, Gen V6.2L, 376ci460465
LT4, Gen V*6.2L, 376ci650650

*Supercharged

Bore and Stroke Combinations

DisplacementBoreStroke
4.8L 293ci3.783.26
5.3L 325ci3.783.62
5.7L 346ci3.893.62
6.0L 364ci43.62
6.2L 376ci4.0653.62
7.0L 427ci4.1254

Compression Ratios

EngineCompression
Ratio
LS110.25:1
LS610.5:1
LS210.9:1
LS310.7:1
LS711.0:1
LT111.5:1

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