Engine-pedia: the ultimate guide to every Gen V LT V8 engine
LAUNCHED with the seventh-generation Corvette in January 2013 the new Gen V V8 ushered in a new era of tech for the venerable small-block. The new LT1 may have held over the capacity, bore and stroke, six-bolt mains, all-aluminium 90-degree construction, 4.40-inch centre-bore spacing, cam location, pushrods and deck height from the LS3, it also brought some huge differences.
On top of a new block and head design, the cooling and oiling systems were radically overhauled and all Gen Vs feature direct-injection. Power was up all over the shop, with the LT5 found in the C7 ZR1 packing 755hp making it GM’s most powerful production car at that time.
An LT1 measures 613mm (24.16in) long, 777mm (30.6in) wide, and 640mm (25.2in) tall, weighing in at 239kg fully dressed. The supercharged LT4 is slightly longer at 685mm and weighs 261kg (576lb) fully dressed, while the LT5 with its bigger supercharger and more complex fuel and oil systems weights over 300kg (700lb).
In the decade since the LT series broke cover GM has released 11 variants, with the new 6.6-litre (400ci) iron-block L8T causing a huge stir amongst enthusiasts looking to build boosted combos off a production block. On the higher tech front the new, naturally aspirated LT6 from the C8 Z06 Corvette brought dual overhead camshafts, 5.5-litres capacity, an 8600rpm redline and an astounding 670hp output. The best came with the C8 ZR1 as GM unleashed a factory 5.5-litre small-block packing a wild 1064hp, and I will post stories on the next-level Gemini-platform LT6 and LT7 on here soon.
If you want a visual representation of how the LT moves the game on above the LS, check out this quick comparison tabe below:
Engine code: L83/L84
Block type: Alloy
Bore size: 3.78”
Capacity: 5.3L
While we commonly think of the Vortec-series 5.3-litre LS “truck” engines as iron block variants, the Gen V changes all this. Now called EcoTec3, both the L83 and L84 5.3s feature alloy bocks and 11:1 comp. Packing 355hp and 520Nm the 5.3-litre Gen Vs use a cast crank and hypereutectic aluminium alloy pistons, and really only differ due to packaging differences in various truck models they’re sold in. Thanks to the direct-injection and cylinder deactivation AFM tech, the L83/L84 in GM light-duty trucks are claimed to be more fuel-efficient than Ford’s turbo six-pot Ecoboost engines.
Engine code: LT6
Block type: Alloy
Bore size: 4.10”
Capacity: 5.5L
Thumping out an amazing 670hp the 5.5-litre LT6 is the world’s most powerful naturally aspirated V8 found in a production car today. Developed for the supercar-fast C8 Corvette Z06 it is an LT almost in name-only thanks to having to fit it into a mid-engined car. Packing chain-driven dual overhead-camshafts, titanium rods and intake valves, 32-valves, a flat-plane crank, dry sump oil system, and 12.5:1 comp it’s a spicy unit. The intake manifold is a giant 11-litre unit packing twin 87mm throttlebodies, meaning the direct-injection squirters ended up side mounted, unlike other LTs. Redline is an amazing 8600rpm.
Engine code: L86/L87
Block type: Alloy
Bore size: 4.06”
Capacity: 6.2L
The new-gen 6.2-litre V8 found in GM’s light-duty trucks, the L86 and L87 are basically the same engine with minor packaging differences to suit the various models they’re sold in. Largely the same as the high-performance LT1, apart from the intake manifold, the 420hp L86/L87 also run 11.5:1 comp and a forged steel crank though it misses out on the LT4’s forged pistons.
Engine code: LT1
Block type: Alloy
Bore size: 4.06”
Capacity: 6.2L
With 460hp, 11.5:1 comp, and a forged steel crank the all-new LT1 brought a fair bit of heat to the C7 Corvette and sixth-gen Camaro. The oil pump runs variable displacement, the cylinder heads are a common design meaning they’re the same on left and right banks, while cylinder deactivation (AFM) and direct-injection bring the pushrod V8 into the 21st Century. GM retained the 4.40in bore-spacing and six-bolt mains, but changed the position of the engine mounts so they don’t bolt-in where an LS was.
Engine code: LT2
Block type: Alloy
Bore size: 4.06”
Capacity: 6.2L
The C8 Corvette’s mid-engined layout created huge packaging headaches for General Motors, so the LT2 rectifies this. Much of the central specs of the LT2 is the same as the LT1, including the compression ratio, bore/stroke, base block specs and head layout, but the cam is more aggressive, it has new intake and exhaust systems to suit the MR placement, and dry sump oil system. This means it pumps out an impressive 494hp.
Engine code: LT4
Block type: Alloy
Bore size: 4.06”
Capacity: 6.2L
With more power than the fabled, hand-assembled LS9 the 650hp LT4 blew minds when it debuted in the C7 Corvette Z06. The compression is 10:1 with forged pistons and rods getting the nod on top of the forged crank. A new, skinnier 1.7-litre Eaton supercharger allowed 9.4psi boost and lower bonnet heights, while the LT4 retained other Gen V signatures like variable valve timing, alloy construction, and direct-injection. The LT4 took over from the 580hp LSA as GM’s go-to supercharged crate motor for years, listing at $US15,000.
Engine code: LT5
Block type: Alloy
Bore size: 4.06”
Capacity: 6.2L
The Corvette ZR1 is known as the fastest production car from GM and the seventh-generation model saw to that with a gigantic 755hp output. The basic specs are largely the same as the LT4, but the main difference happened up top, with the 2.65-litre supercharger offering nearly a litre extra capacity over the LT4’s pump. The 2650 blower is so big it meant the LT5 runs port injectors as well as direct-injection just to keep up with the fuel demand. With the C7 ZR1 long out of production, these days the LT5 is offered as a crate motor.
Engine code: LT376
Block type: Alloy
Bore size: 4.06”
Capacity: 6.2L
The LT376 is essentially an LT1 that GM sells as a higher performance crate motor. Packing the LT Hot Cam (228⁰/248⁰ duration) and CNC-ported cylinder heads it lifts the LT1’s horsepower up 75hp as it throws down 535hp. The LT376 is available alongside several other LT engines as part of Chevrolet’ Performance’s crate engine program, including the 650hp LT4 and big-banger 755hp LT5.
Engine code: L8T
Block type: Iron
Bore size: 4.05”
Capacity: 6.6L
The only iron-block LT engine and the biggest-capacity Gen V (6.6-litres or 400ci in the old money), the L8T is GM’s answer to Ford’s 7.3 Godzilla. Used in heavy-duty trucks the L8T’s forged crank and 3.89 stroke differs from the other LT truck motors, while the intake manifold and cam are geared for lower-RPM torque production. Though it only lists at 401hp stock, the L8T block and crank are already available from Chevrolet Performance as aftermarket accessories, which will be used for boosted builds soon no doubt.
FITNESS IN
IF YOU’RE fixin’ to slap an LT5 in where your LS1 or LS3 used to be, then you’re in for some surprises. Firstly, GM changed the engine mount bosses on the side of the LT blocks so you’ll need to make new engine mounts when swapping from an LS to an LT.
The cylinder heads are an all-new design as GM had a heck of a job fitting valves, a spark plug and a fuel injector into the combustion chamber. They’re universal castings, which means the left and right are the same, but the orientation of the intake and exhaust valves has been reversed compared to a traditional LS head. This Will require new headers for a car previously fitted with an LS, while you’ll also need a Gen V-fitment intake manifold as the LS item won’t fit.
They do share the same reluctor wheel tooth count on the crank, but the electronics required to run all the factory functions of an LT isn’t as simple thanks to the variable valve timing, Active Fuel Management, direct-injection and more.
There is good news for those wanting to mix and match their LS and LT hardware, as the aftermarket is now selling tools which make it easier to fit an LS top-end on your LT short motor, or vice versa. While the head bolt-pattern and water jackets line up between LS and LT heads, the locating dowels have moved from the lower outer position (LS) to upper outer (LT).
This doesn’t resolve the issue with piston-to-valve clearance on the high-compression LT engines. There is also the issue of the Gen V camshaft, which features a unique eccentric at the back of the shaft to drive the mechanical DI fuel pump, and this means you’d likely need to swap to a new cam and lifters at the same time.
WHAT’LL SHE DO, MISTER?
LOTS, Little Timmy! One of the many big upgrades the Gen V enjoys is gussetted water jackets in the aluminium blocks, as these add a great deal of strength. While alloy Gen IV blocks are known to tap out around 700hp, the alloy LTs are known for nudging 1000hp thanks to better stability in the platform.
So far we haven’t seen enough iron L8T builds taken to the limit to say what they can handle with any certainty. The 12mm head bolts (larger than the 11mm used in LS) should provide better clamping to handle boosted combos, while GM has also worked on eradicating windage issues from the LS, which always suffered in this area due to the deep-skirt design of the blocks.
