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LT1 Engine
Inside the LT1 Title Typography
Everything You Need to Know About the Next-Gen Small-Block Chevy

BY Ryan MansonPhotography BY THE AUTHOR

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ince its introduction in 1955, the small-block Chevy engine has become the favorite amongst hot rodders, muscle car builders, and classic truck enthusiasts. Its compact size and efficient weight-to-power ratio has made it the perfect powerplant to replace a gangly six-cylinder, heaving big-block, or wheezing Flathead. Consistently upgraded over its 40-plus year lifespan, it’s easy to imagine that when its successor was introduced in 1997, it wasn’t without its share of naysayers. Yet while still retaining a very similar design to the original small-block Chevy (4.40-inch bore centers, in-block camshaft, overhead valves, and so on), the LS1 was a complete, clean sheet redesign that was as revolutionary then as the original 265ci engine was in 1955. An aluminum, long-skirt engine block with six main cap fasteners, high-flow cylinder heads that favored higher revs, and a lightweight, composite intake manifold were all truly state-of-the-art features that helped the LS engine family usher in the 21st century.

But as the small-block evolved into different iterations over the years, so too would the LS, eventually maturing into a monster 7.0L LS7, the largest displacement production Chevy small-block ever produced, and the 638hp 6.2L supercharged LS9, Chevy’s most powerful small-block ever at the time!

After dominating the landscape for nearly two decades, history repeated itself yet again when GM introduced one of the most technologically advanced engines in the world, the 6.2L Gen 5 LT1 small-block engine. Drawing from Corvette’s long LT-series lineage dating back to the first LT1 in 1970, the latest LT1 was engineered to be best in class in many categories by incorporating next-gen technologies, like direct fuel injection and a radically redesigned combustion chamber with 11.5:1 compression ratio. This makes the LT1 not only an extremely efficient package but the most powerful one GM’s ever produced for the Corvette with the highest base horsepower (460 hp) and torque (465 lb-ft). Yet while the LT1 and the original 265 small-block Chevy is like comparing a flat screen OLED TV to a black and white Trinitron, the LT1 still features the traditional 16-overhead valve, cam-in-block, 90-degree V-8 engine design just like its predecessor did nearly 60 years prior.

Exploiting their massive 450,000-square-foot powertrain development center, GM spent five years and consumed 0.1 quadrillion bytes of disc space worth of computational analysis. That’s the equivalent of 18 billion typed pages or 23,000 DVDs! As one can imagine, development such as this can be a tedious affair, with more than 75 iterations of the combustion system alone being developed and evaluated before the final design was selected. The resulting cylinder head is a brand-new design featuring a special dished piston. Together they work to exploit the high compression, mixed motion parameters enabled by direct injection. Another significant design change, though not outright noticeable, is the reversal of the position of the valves in the cylinder heads. This change, along with an entirely new intake manifold design, enables a straighter path for the air intake charge into the combustion chamber. Large, 2.13-inch hollow intake valves bring fresh air into the cylinder while 1.59-inch hollow sodium exhaust valves help expel the consumed mixture. Moving the spark plugs closer to the center of the combustion chamber also helps the LT1 push the combustion flame front to the center as well, increasing the direct injection system’s efficiency. By the time of its release in 2014 the Gen 5 LT1 engine had accumulated an equivalent of over 1.5 million miles of validation testing.

When GM dropped the LT1 engine in 2014 for the C7 Corvette, we knew they were onto something special, all the while playing their cards close to their chest. Fast-forward a good eight years later and the LT-series engine has found itself in a number of GM offerings, from Cadillacs to Camaros to Silverados, undoubtably becoming the latest small-block Chevy to dominate the space. With that passage of time and the wider variety of vehicles that have received the new LT1-series engine, we’re starting to see these motors pop up in the local classifieds, online parts trader pages, and under the hoods of classic trucks. But what makes the LT-series engines so special and sets them apart from their predecessor can’t be described. It takes a closer look inside the next-gen small-block Chevy to see what makes them tick and why you might want to drop one between the ’rails of your classic truck.

precision cast-aluminum engine block
precision cast-aluminum engine block
1-2. A close-up look at the LT1 begins with the CNC-machined 391 precision cast-aluminum engine block. Like its predecessor, the fifth-gen small-block retains the same 4.40-inch bore centers and a cam-in-block design, but that’s where the similarities end. Cast-in-place cylinder liners utilize induction heating for dimensional control, resulting in an all-aluminum deck face and exact cylinder placing. While the LS-series engines came equipped with powdered metal main caps, the LT1 features nodular iron mains, retained via six crossbolts.
LT1 rectangular-port
LT1 rectangular-port
3-4. When it comes to the LT1 rectangular-port, direct fuel injection cylinder heads, the location of the valves have been reversed as compared to the LS-series engine, which enables a straighter path for the air charge into the combustion chamber. But the differences between the two doesn’t end there. With the direct injection system as its centerpiece, the LT1 combustion chamber is a complete clean-sheet design, featuring 2.130-inch intake and 1.590-inch exhaust valves, splayed 2.5 degrees to the spark plug and fuel injector, and is the result of 6 million hours of CPU time. Roller trunnion–equipped, non-roller investment-cast rocker arms, meanwhile, prove that simple designs don’t always require a complete redesign.
fifth-gen’s new combustion system
5. So advanced was the development of the combustion chamber design that an SAE paper was written covering the process. Designers had to start from scratch when it came to the design of the fifth-gen’s new combustion system since the overhead, two valves per cylinder arrangement is completely different than the DOHC design of GM’s other direct-injected engines. The flow field, the motion of the air/fuel mixture, is more complex with an overhead valve design and direct injection requires more mixture swirling for optimal combustion. To deliver on the horsepower, torque, and efficiency goals for the engine, GM engineers developed and evaluated over 75 different combustion chamber designs through computational analysis to establish the optimal placement of the injector in relationship to the spark plug within the combustion chamber, the optimal size and angle of the valves, the size and volume of the combustion chamber, and the configuration of the piston dome, which is crucial in supporting direct injection combustion.
piston
6. One of the most cutting-edge aspects of the LT1 engine, the combustion chamber and direct fuel injection system, unsurprisingly required a complete redesign of the piston as well. In order to bump the compression up to the required 11.5:1, a high-compression “pop-up” dome was utilized with valve reliefs machined to ensure proper clearances. This dished piston design complements the small combustion chamber of the head and works to exploit the high-compression, mixture motion parameters enabled by direct injection. The pistons also feature “risers” at the top to direct the fuel spray for more complete combustion.
hypereutectic aluminum piston
7. The hypereutectic aluminum pistons are mated to forged powdered metal connecting rods with features more akin to a supercharged setup than a naturally aspirated one, providing plenty of bottom end power to support its high-compression ratio.
A forged steel crankshaft with a 3.622-inch stroke
8. A forged steel crankshaft with a 3.622-inch stroke supports the rotating assembly and features a 58x reluctor wheel. Polymer-coated Bi-metal eccentric bearings provide all lubricated surfaces (main and rod bearings).
Eight oil-spraying jets drench the underside of each piston and the surrounding cylinder wall
9. Eight oil-spraying jets drench the underside of each piston and the surrounding cylinder wall, providing additional piston cooling and promoting extreme output and durability.
LT1’s camshaft
10. The LT1’s camshaft features 242 degrees of intake timing and 244 degrees of exhaust at 0.050 inch. Based on LS7 specs, the LT1 features new high rocker ratio and splayed valve geometry. That strange tri-lobe at the rear of the camshaft drives the direct-injection fuel pump. The LT1 also features variable camshaft timing, which can vary the camshaft position versus the piston position. At idle, the cam is at its fully advanced position, allowing for exceptionally smooth idling. Under other driving conditions, the phaser adjusts to deliver optimal valve timing for performance, driveability, and fuel economy. At high rpm, it may retard timing to maximize airflow and increase horsepower. Alternatively, at low rpm, it can advance timing to increase torque. In front of the camshaft reluctor wheel is the vane-type phaser, responsible for adjusting the timing of valve operation on the fly.
the standard dry-sump setup as utilized in the production C7 Corvette and a wet sump design
A redesigned windage tray is utilized in addition to a new oil scraper designed to enhance performance and efficiency by improving oil flow control and bay-to-bay crankcase breathing
11-12. When it comes to the oiling system, the LT1 crate engine is offered in two different versions; the standard dry-sump setup as utilized in the production C7 Corvette and a wet sump design. A redesigned windage tray is utilized in addition to a new oil scraper designed to enhance performance and efficiency by improving oil flow control and bay-to-bay crankcase breathing.
Cylinder parts
Engine illustration
13-14. The wet sump oil system utilizes a variable displacement, two-stage vane-type oil pump assembly, mounted on the front of the engine block, and driven directly by the crankshaft sprocket. An oil control solenoid valve, controlled by the ECM, is mounted to the oil pump and provides two-stage functionality to maintain proper lubrication and minimize excessive oil delivery to the cylinder heads and PCV system.
direct injection system
direct injection system connected to engine
Engine put together
15-17. Hidden under the intake manifold is arguably the LT1’s most advanced feature, the direct injection system. Fed by a high-output mechanical fuel pump, eight suspended injectors spray fuel directly into the combustion chamber. An internal, solenoid-controlled valve regulates the high fuel pressure controlled by the ECM.
intake manifold
18. The “runners in a box” intake manifold design is a four-piece, molded and welded composite that is more lightweight and thermally efficient than previous aluminum designs. A low-restriction, drive-by-wire, 87mm digital throttle body feeds fresh air into the manifold in an extremely efficient manner.
A pair of proprietary tuned cast four-into-one short-header exhaust manifolds
Engine side profile
19-20. A pair of proprietary tuned cast four-into-one short-header exhaust manifolds feature nearly equal-length runners to ensure even expulsion to excise the used air/fuel mixture. Optimized runner geometry was developed using the latest analysis software to develop cross sections that minimize restriction and maximize volumetric efficiency tuning of the exhaust gas flow.
As delivered from Chevrolet Performance, the LT1 requires a couple upgrades/additions when used in some classic truck applications.
21. As delivered from Chevrolet Performance, the LT1 requires a couple upgrades/additions when used in some classic truck applications. A keen eye notices the lack of a power steering pump due to the fact that the C7 Corvette utilizes electric power steering. The other issue that arises relates to the variable displacement A/C compressor that is incompatible with most aftermarket A/C systems.
fabricating one-off solutions that allowed us to mount a standard Type-II power steering pump and a Sanden SD-7 A/C compressor
22. We solved this issue by fabricating one-off solutions that allowed us to mount a standard Type-II power steering pump and a Sanden SD-7 A/C compressor. Thankfully, the aftermarket has caught up with the LT-series developments, with many companies offering off-the-shelf solutions for these two problems.
components for our LT1 crate engine package
23. Here are the components for our LT1 crate engine package. From left is a pair of wideband O2 sensors and install bungs, drive-by-wire throttle pedal assembly, fuse/relay center, engine control module (ECM), mass airflow sensor and install bung, fuel pressure sensor, and fuel pump driver module. Also included in the LT1 crate package is the engine harness that connects the myriad of sensors and systems on the engine to the ECM. The fuse/relay center includes relayed circuits that provide power for an electric fuel pump to feed the high-pressure direct-injection pump and two electric fan circuits programmed to turn on individual fans at 207 and 221 degrees F.
LT1 engine sits nicely between the rails of our Squarebody Chevy Roadster Shop SPEC-series chassis
24. Our LT1 engine sits nicely between the rails of our Squarebody Chevy Roadster Shop SPEC-series chassis. That Procharger hanging off the driver side of the engine hints at things to come …
Chevrolet Performance
chevrolet.com/performance
Clampdown Competition
clampdowncomp.com
Roadster Shop
(847) 949-7637
roadstershop.com