Rebirth Of The Gen V LT1 Small-Block...Part Two!

For the launch of the all-new fifth-gen small-block, Chevrolet resurrected one of the oldest names in the Mouse motor's history.

Patrick Hill Mar 11, 2013 0 Comment(s)
Gm Gen V Lt1 Small Block Sketch Cutaway 2/16

A lot of things have taken place in the last couple of years that have could heralded the death knell of the performance V-8 in a factory-built car. Ever tightening emissions standards, brutal government mandated increases in CAFE (Corporate Average Fuel Economy) requirements, skyrocketing gas prices, and a sluggish economy are not on the side of an automaker keeping a big V-8 in its production lineup. Thankfully we have those at GM who relish a challenge against the most iconic engine platform ever, and take pure pleasure in defeating the enemies of factory V-8 performance in brutal smack downs of horsepower and cubic inches.

In the mid-'90s, many in the industry thought the folks at GM/Chevrolet were crazy in sticking with "archaic" pushrod technology instead of following the overhead cam craze of other brands. Just another example of GM's stubbornness in clinging to outdated technology and not keeping up with modern times. Well, the Gen III and Gen IV "LS" series V-8 left many a doubter lying on the floor with its great fuel efficiency, power output, compact size, light weight, low production costs, and overall versatility. For the 21st century small-block, the engineers behind the Bow Tie seem to have done it again.

Since the pending announcement of the new Gen V small-block hit the internet, there've been a lot of rumors and erroneous details about the new engine that left no real clear picture about what the new Mouse was going to be, outside some sort of V-8. Overhead cams, twin in-block camshafts, three valves per cylinder, 5.5 liter or smaller displacement, factory turbos—the rumors were all over the place.

Well, we went to Michigan when GM unveiled the Gen V engine, which will be introduced first in the all-new '14 Corvette. When the cover was lifted, all the rumors vanished, and in their place was a brand-spanking-new 6.2 liter, all-aluminum, direct injected, constant variable valve timing-equipped V-8, with a name all Chevy enthusiasts remember with both fondness and derision: LT1.

LT1? Judging from the reactions when we first posted the new designation to our Facebook page, reactions were mixed. Negative or positive, it doesn't matter. The new engine shares only four parts with the LS series (more on that later), promises great out of the box horsepower, even greater potential for more, and is probably the best rebirth possible for one of the more storied engine names in Chevy's RPO list. So, leave the Opti-fail jokes in the back seat of your '94 Z28, and get ready for what could be the best small-block to ever leave Detroit.

According to one GM spokesman we spoke to, the name still resonates inside Chevrolet. The original from 1970-'72 is considered by many to be the best small-block ever—big-time horsepower like the fuel-injected V-8s that came before it, but with lots of bottom-end torque. When the second-gen LT1 was introduced in 1992, it was the first high-performance V-8 to produce 300 hp since 1971 and was seen as the second coming of all-out performance in the modern era. Because the new engine is being introduced 22 years after the Gen-II small-block (which came 22 years after the first LT-1) it seemed only logical to Chevy to call it this.

Here's the overview: 6.2 liters, direct injection, 11.5:1 compression, specially-designed pistons for maximum combustion efficiency, a lower profile intake, constant variable valve timing, cylinder deactivation (V-8 to V-4), 450-horsepower (perhaps more), the lowest emissions from a large displacement V-8 to date, and the promise of unequaled fuel economy. And it's all wrapped up in an aluminum package.

Gm Gen V Lt1 Small Block Original 1970 Lt1 3/16

The original LT-1 debuted in the ’70 Corvette (370-hp) and Camaro Z28 (360hp), and was the most powerful carbureted small-block ever installed in a production car.

"The Holy Grail for developing a performance car is delivering greater performance and more power with greater fuel economy, and that's what we've achieved," said Tadge Juechter, Corvette chief engineer. "By leveraging technology, we are able to get more out of every drop of gasoline, and because of that we expect the new Corvette will be the most fuel-efficient 450 horsepower car on the market."

Only 450 hp? That's just 14 more than the current Vette's LS3 with the dual-mode exhaust, isn't it? Well, don't be surprised if that number goes up. The 450 HP rating given to us is a preliminary estimate from early testing, and once full testing is finished up with the usual amount of tuning and tweaking from the engineers, that rating will probably go up. Though the new LT1 is only months away from production, there's a little more development work to be done. And as we've seen from the LS3, this number could be seriously underrated.

Something else we noticed when checking out the front accessory drive on the new LT1 … no power steering pump. The engineers didn't say anything, but we can only surmise this means the C7 will feature electric power steering. Another interesting item is the cast iron exhaust manifold. Its construction and outlet flange, which mimic that of the current LS7 V-8, look conspicuously ready to accept an exhaust driven power adder of some sort. Could the next ZR1 have a turbo or two? Just a guess based on observations, so we'll be forced to wait and see till this time next year.

Here's what the engineers have to say:

"The Corvette LT1 represents the most significant redesign in the small-block's nearly 60-year history—building on its legacy to make one of the world's best engines even better," said Sam Winegarden, vice president of Global Powertrain Engineering. "More than just great horsepower, the LT1 has been optimized to produce a broader power band. Below 4,000 rpm, the torque of the Corvette LT1 is comparable to that of the legendary 7.0L LS7 out of the current Corvette Z06. The LT1 is a sweetheart of a powerplant, and drivers will feel its tremendous torque and power at every notch on the tachometer."

Increased power and efficiency were made possible by an unprecedented level of analysis, including computational fluid dynamics, to optimize the combustion system, the direct injection fuel system, active fuel management, and variable valve timing systems that support it. More than 10 million hours of computational analysis were conducted on the engine program, including 6 million hours (CPU time) dedicated to the advanced combustion system.

Direct injection is all-new to the engine architecture, and is a primary contributor to its greater combustion efficiency by ensuring a more complete burn of the fuel in the air-fuel mixture. This is achieved by precisely controlling the mixture motion and fuel injection spray pattern. Direct injection also keeps the combustion chamber cooler, which allows for a higher compression ratio. Emissions are also reduced, particularly cold-start hydrocarbon emissions, which are cut by about 25 percent.

Gm Gen V Lt1 Small Block Gen Ii 1991 Lt1 4/16

The second small-block bearing the LT1 RPO came out in the fall of 1991, first powering the ’92 Corvette, then the new ’93 Camaro. In the Vette, the LT1 was good for low 13s in the quarter-mile and a top speed of over 160. While a potent performer in its day, the second LT1 was plagued by reliability issues with its cam-driven water pump and Opti-Spark ignition system.

Active Fuel Management (AFM)—a first-ever application on Corvette—helps save fuel by shutting down half of the engine's cylinders in light-load driving. At cruise speeds and in light load driving, the LT1 will shift from a V-8 to a V-4.

Continuously variable valve timing, which GM pioneered for overhead-valve engines, is refined to support the LT1 AFM and direct injection systems to further optimize performance, efficiency and emissions.

These technologies support the all-new, advanced combustion system, which incorporates a new cylinder-head design and a new, sculpted piston design that is an integral contributor to the high-compression, mixture motion parameters enabled by direct injection.

The LT1 head features smaller combustion chambers designed to complement the volume of the unique topography of the pistons' heads. The smaller chamber size and sculpted pistons produce an 11.5:1 compression ratio, while the head features large, straight rectangular intake ports with a slight twist to enhance mixture motion. This is complemented by a reversal of the intake and exhaust valve positions, as compared to the previous engine design. Also, the spark plug angle and depth have been revised to protrude farther into the chamber, placing the electrode closer to the center of the chamber to support optimal combustion.

The pistons unique top design was optimized via extensive analysis to precisely direct the fuel spray for a more complete combustion. The contours of the piston heads are machined to ensure dimensional accuracy, essential for precise control of mixture motion and the compression ratio.




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