It wasn’t that long ago that the words “crate engine” were tainted by an element of shame. What kind of hot rodder buys an engine that’s already built? “A true gearhead builds his own engine” was the typical knee-jerk response, but ever since the arrival of Chevy’s LS small-block engine a quarter-century ago, that has gradually changed. LS crate engines are all the rage now, and when we look at the history of the LS small-block, we can see that a steady march of mechanical development along with the evolution of the engine’s design brief has resulted in a tremendous jump in power. It has also resulted in a proliferation of different versions—46 production variants in all, if we count Gen IV and Gen V—and their parts can’t always be relied on to interchange.

The LS engine is best imagined as an evolving series of different small-block V-8 engines with some shared parts, the most critical components being the engine block and cylinder heads, followed by the camshaft/valvetrain, and rotating assembly. As the aftermarket has adapted to changes made at the factory over the past 25 years, its focus has narrowed down the performance variants of the LS engine family such as the popular rectangle-port LS3/L92, helping hot rodders and engine builders target their performance efforts to the factory variants that pay the biggest dividends. In some cases, the aftermarket has altered the basic LS design to make it more robust in some areas, a great example of this being Dart Machinery’s LS Next block, which is different enough to the point that it technically isn’t a Chevy LS engine any more.

To the uninitiated, parts ordering to build or finish an LS engine can seem like a secret language with a steep learning curve and a high out-of-pocket cost for getting it wrong. Fortunately, you’ve come to the right place; if you appreciate really big horsepower and if you know the value of a dollar, these six LS crate engines are the most powerful units currently being produced and have the highest bang-for-the-buck.

BluePrint 625 hp/427 cu-in LS Retrofit Crate Engine

Price: $11,999.99

BluePrint Engines is a bulk builder of crate engines and the company’s focus is typically on modestly-priced high-value offerings that are widely sold as commodities at big-box outlets. With the company’s BP4273LS 427 cu-in offering, however, BluePrint pulls out all the stops, with a new Chevy LS3/L92 block stuffed with a fully forged 427 cubic-inch rotating assembly (typically, this is 4.0000-inch bore x 4.125-inch stroke). With a compression ratio of 11:1, it’s a naturally aspirated combo that makes an honest 625 hp and 565 lb-ft of torque using a .624-inch lift hydraulic roller cam with 239/255 degrees duration at .050-inch lift and a set of BluePrint’s proprietary 72cc chamber rectangle-port heads (2.165-/1.600-inch diameter valves).

The powerhouse crate engine comes fully assembled with an LS3 intake manifold, 87mm DBW throttle body and throttle pedal, balancer, 42 lb/hr injectors, coil packs, ECM (including calibration), and includes individual dyno testing and a 30-month/50,000-mile warranty. BluePrint also offers versions of its 427 cubic-inch LS stroker crate engine with a high-end billet aluminum accessory drive set-up ($14,299, here), and an 800 hp Magnuson supercharged version (starting at $19,299 here), but the best price we found for the 625 hp version was offered through Classic Industries for $11,999.99. (We noted that the crate engine model number was off by one digit; the specs are otherwise the same, but you may want to put in a call before ordering as some of the details may be updated).

Chevrolet Performance 627 hp LSX 454 Crate Engine

Price: $12,148.97

On its website, Chevrolet Performance says its LSX 454 crate engine (part No. 19355573) is big-block power for the 21st century, and at 627 hp (6,300 rpm) and 586 lb-ft (5,100 rpm) you can believe them. Our search dug up a number of storefronts that sell the LSX 454 crate engine, but Texas Speed is currently offering it for $12,148.97, so it may pay to shop around some. Like the BluePrint Engines’ 625 hp/427 cu-in offering, the Chevy Performance LSX454 contains a fully-forged rotating assembly (11:1 compression, 4.185-inch bore x 4.125-inch stroke), but uses a Chevy Performance part No. 19260099 Bowtie Block, otherwise differentiated from a production LS7 block with its cast iron construction and extra beefcake in lower bulkhead areas. Critically, the LSX 454 crate relies on a pair of as-cast 70cc LS7 production cylinder heads which feature CNC porting from the factory as well as 2.200-inch titanium intake valves and 1.610-inch diameter sodium-filled exhaust valves. Matched to the LS7 heads is a hydraulic roller cam with specs of .648-inch lift and 236/246 degrees duration at .050-inch valve lift.

Note that the Chevy Performance LSX454 is a partial long-block designed in large part for racers and specialty builders who often have class-specific limitations or space constraints; you will still need to pair it with the rectangle-port intake manifold, throttle body, injectors, and ECU of your choice. Based most closely on the specs of the discontinued production LS7 (2006 to 2015), the LSX 454 differs in that it does not have the LS7’s aluminum block, titanium connecting rods, intake, or dry-sump lube system, but it does have additional beef in the bottom end to handle a power adder such as nitrous oxide or a supercharger kit. This is an engine you’ll need to customize to your liking, making each installed version different.

Chevrolet Performance 650 hp/6.2-liter LT4 Crate Engine

Price: $14,817.76

Moving up the pecking order into the power-adder ranks we find another Chevrolet Performance offering, the 650 hp LT4 dynamo that powered the C7 Corvette Z06 from 2015 to 2019. We were sad to see Chevy Performance kill the 755 hp LT5 crate engine—the ground-breaking powerplant found in the 2019 Corvette ZR1—earlier this year, but that engine was sadly discontinued after just a two year run. As a consolation of sorts, Chevy Performance is still offering the LT4 crate engine with its more modestly sized 1.7-liter intercooled supercharger (versus the LT5’s Eaton-sourced 2.65-liter unit), a fact that arguably benefits a heavier street car with the need for lots of torque that comes on hard and turns on early. Some might quibble with the fact that the LT4 is technically a Gen V small-block and not an LS-based Gen III or Gen IV, but the efficiency improvement in the form of direct injection does make the LT4 the most technically advanced engine of our group.

Internally, the LT4 crate engine relies on the Z06’s stock internals, which include a 6.2-liter aluminum block (376 cu-in) and a fully-forged rotating assembly (10.0:1 compression) with a hydraulic roller cam that specs out at a very mild .492-/.551-inch lift and 189/223 degrees duration at .050-inch lift. This is a completely stock turnkey Z06 mill with great streetability (you’ll still need a harness, ECM, and flywheel), so it features factory LT4 rec-port cylinder heads (2.13-/1.59-inch valves, 65.5cc chambers) and runs on ordinary 91-octane pump fuel. The advantage here is that as a production Corvette piece, this reactor core is built to take all the punishment of a street car and it even comes with a 12-month/12,000-mile warranty. We recently found the LT4 crate engine at Summit Racing here for $14,817.76, but this is a commodity item, so it may pay to shop around.

Boost District 750 hp LSX376-B15 LS Crate Engine Package

Price: $15,950.00

If you lamented the sudden disappearance of Chevrolet Performance’s 755 hp LT5 crate engine (which previously sold for $19,995), wipe those tears away and take a gander at Boost District’s 750 hp LS crate engine package, which sells for roughly $4,000 less than the LT5 had sold for. Still cryin’? Tick the box for the company’s higher-boost 860 hp version at $17,750. Like all the engines in this guide, there are no junkyard parts here; this one starts with a brand-new boost-ready Chevrolet Performance LSX376-B15 partial long-block, which has an all-forged rotating assembly (9.0:1 compression) and an un-boosted power rating of 473 hp. This rating, however, hides this engine’s true intention as a do-it-your-self Lego kit for big boost (or alternately, the perfect low-compression crate engine in a world with a sketchy fuel supply), which Boost District finishes with one of their 13 psi Eaton TVS2650 supercharger kits.

This Eaton-derived TVS rotor pack is the same one found in the LT5 that is so popular in the aftermarket; it’s a perfect complement to Chevrolet Performance’s 6.2-liter LSX376-B15 crate engine, which was designed for combos just like Boost District’s. The base crate engine’s “B15” designation stands for 15 lbs. of boost; its boost-specific application incorporates a boost-optimized compression ratio of 9.0:1 and a hydraulic roller cam spec’d at .560-/.555-inch lift and 210/230 degrees duration at .050-inch lift. We’re not positive this is a completely assembled crate engine despite the photo; it looks like you’ll have to complete the blower bolt-on yourself, but to us that’s more fun than it is a hassle. This package comes with the assembled LSX376-B15 partial long-block ($9,197.50), the Boost District TVS2650 supercharger kit ($9,750), and fuel injectors with billet aluminum fuel rails. As you can see by the individual item prices, buying the Boost District combo package presents a huge cost savings. Note: A three-row accessory drive kit, stand-alone ECU, and wiring harness are available at extra cost.

Prestige Motorsports 800+hp Supercharged 427 cu-in LS Next Crate Engine

Price: $29,999.00

Every engine has its limits, and for the LS the weakest link after the cast crank and hypereutectic pistons is the block. Where a forged rotating assembly was all that was needed up to this point (excluding airflow and fuel requirements), Prestige Motorsports’ 800-plus hp LS crate engine accesses even higher power levels with the extra step of an improved aftermarket cast-iron block. The bulwark for that kind of power can only come from something like Dart Machinery’s LS Next SHP cast-iron cylinder case, and the 100-lb penalty for the cast iron block is definitely worth it for this kind of power and reliability in a pump-gas street machine. In this package, Prestige has us covered with strength to spare.

Inside, the Dart LS Next SHP block has been endowed with a four-inch stroke forged crank, 4340 forged steel rods, and 4.125-inch bore 2618 forged pistons (9.5:1), then topped with proprietary CNC-ported rec-port LS3 cylinder heads with 2.165-/1.590-inch valves and upgraded steel roller-trunion rocker arms activated by a hydraulic roller cam of proprietary spec. Feeding the beast is a 2.9-liter Whipple supercharger. At a price one dollar shy of the $30,000 mark, the package is remarkably complete and includes Holley’s Terminator X MPFI fuel injection, Holley Smart coils (relocation kit included), and a Concept One 10-rib drive system. Each Prestige Motorsports crate engine is dyno’d and comes with a three-year/unlimited-mile warranty.

Nelson Racing Engines 1,100 hp Twin-Turbo Alien 427 cu-in LS Crate Engine

Price: $34,999+

If you’ve made it to the bottom of the page, congratulations! You have excellent taste in automotive machinery; for the same cheddar as a two-bedroom home in Oklahoma, you can have an 1,100 hp twin-turbo pump-gas 427 cu-in LS crate engine built by Nelson Racing Engines, the SoCal-based engine builder to the rich and famous. And here’s a little secret: if you’ve got more cheese in your pocket, you can go higher than 1,100 hp. A lot higher. NRE custom-builds each engine, so you’re not limited to components, boost, accessories, or fuel octane.

In the universe of Nelson Racing Engines, nothing is out of the realm of possibility, from twin turbos and superchargers to literally any engine family or induction type you want. In the LS stable, NRE offers five programs, all on the Dart Machinery LS Next block (9.24-inch deck height) and with Dart’s 280cc Pro 1 cylinder heads. Two of those programs offer Whipple superchargers (2.9-liter and 4.0-liter versions) and three offer twin-turbos, which is our choice here. The twin-turbo Alien LS 427 is the company’s middle twin-turbo offering and is significantly developed for street use on 91-octane fuel, though NRE points out power goes from 1,100 hp to 1,500 hp with a change to higher-octane race gas and some tuning. There are too many options to mention here (you really need to click on their page to see the variety), but it is possible to go all the way up to 2,000 hp if you’re so inclined.

Watch the Full Episode of HOT ROD Garage! Adding 150 Horsepower to a Junkyard 6.0L LS

On this episode of HOT ROD Garage, Lucky Costa’s personal ’66 Chevelle gets major upgrades to its 6.0L LS truck engine. Tony Angelo and Costa install a set of AFR heads and a Magnuson supercharger on this high-mileage, well-worn engine to really wake up the powerplant. Without any upgrades to the 100,000-plus-mile bottom end, the #66ChevHell puts down more than 500 whp! Sign up to MotorTrend+ today and start watching every episode of HOT ROD Garage—and much more!

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