It’s the new kid/engine on the block. The gasoline direct injection (GDI) LT1 made its appearance in the 2014 Corvette, quickly followed by its supercharged LT4 cousin making a killer 650 hp. Let’s not run past this point—a production engine making 650 hp. And that’s rated using the newer net correction factor. In the performance world where we live, the “hot rod” correction factor adds another 5 percent—making this LT4 somewhere around 680 hp. But you don’t have to buy a new Corvette to get one.
It wasn’t long before this engine appeared in the Chevrolet Performance catalog as a crate engine. It’s not cheap—the wet-sump version comes in at just under $13K. But where else can you find this kind of technology for that kinda cash? This is man-sized power trickling down from GM’s engineering mountaintop that you can have dropped off at your garage door.
It’s no secret that the typical street guy may not be ready for GDI technology. There’s been some understandable trepidation. GDI engines are a completely new animal, but then so was the LS1 when it first appeared in 1997. Yes, the LT1/LT4 engines are significantly different, which is why GM labeled this family as Gen V. But really, the Gen V’s have much in common with their Gen III/IV gene-pool cousins. The LT1/LT4 is still a two-valve, pushrod, V-8 with coils for each cylinder and electronic throttle control. So what’s not to like?
But don’t be fooled—the Gen Vs will take time to settle in and become accepted. Luckily, there are a few intrepid souls who have embraced this Gen V engine and are not afraid to boldly take on the challenge. That’s the focus of our story. Our friends at Galpin Auto Sports (GAS) in Van Nuys, California, recently took in a ’67 Chevelle from customer Robbie Schaeffer who was tired of the car’s current 572ci carbureted crate engine. He was desirous of Rat power with some late-model sophistication. The LT4 was the perfect solution.
Magazine stories have an unfortunate habit of making complicated efforts look easy. This is a byproduct of having to condense a fairly complicated three-dimensional effort into a series of simple, two-dimensional photographs each with a short, concise caption. All of these photos are as accurate as we can make them. But what is difficult to portray here is the hundreds of hours put into fabricated brackets, tubing, mounts, adapters, and creativity that fill in the white space between each of these photos.
Realistically, there’s probably a 300-page book where we could write about every little detail of how this hybrid went together. We discovered this build after it had begun when our friend Scott Gillman hired on at GAS as a fabricator and creative consultant along with fellow fabricator Eric Simpkins.
We will hit the highpoints but itemizing every detail isn’t possible with these few pages. Perhaps the most important point is that available real estate was problematic almost from the beginning. Keep in mind GAS was installing a wet-sump engine. The dry-sump LT4 version would have been even more difficult when faced with the issue of finding space for the dry-sump tank and routing the plumbing. It was a major challenge just finding room for the electronic controllers and the wiring. This may seem like a small thing, but the overall project demanded hundreds of hours of fabrication work to produce the results presented here.
As more GDI swaps are attempted, more information will begin to disseminate—just like it has for the Gen III/Gen IV engines. There will no doubt be future solutions that will make this swap seem far less daunting. But for now, we’ll start right here. So climb in and hang on as we take you for a fun ride down LT4 Swap Alley.
Just know we don’t paint too dismal of a picture, the Chevelle is now running and Schaeffer is having a ball with his new machine. Because the GM spins the smaller blower fast, this engine makes 625 lb-ft of torque at only 2,800 rpm. That’s an astonishing amount of torque at just above stall speed for a typical street converter. Needless to say, the Chevelle is a tire annihilator.
1. Fitting the current generation LT4 supercharged engine into a ’67 Chevelle is quite an undertaking. Galpin Auto Sports (GAS) took on the challenge.
2. The Chevelle’s owner, Robbie Schaeffer chose a wet-sump LT4 Chevrolet Performance crate engine for the swap. In the second photo, Gillman has already converted the accessory drive over to include a hydraulic power steering pump. It’s possible that Galpin may offer this as a retail product since they created the CNC pattern and determined the proper pulley and belt length.
3. The GAS crew quickly determined that the LT1/LT4 motor mount pattern is not the same as the Gen III/IV. GAS made its own adapter mounts, but we found some online at a company called ICTBillet.com. The -12 hoses from the LT4 oil pan are to the external oil cooler.
4. The Chevelle came with a 4L80E automatic, which uses the traditional SBC/BBC bellhousing bolt pattern. The LT1/LT4 changed the top bolt position from the Gen III/IV slightly. This wasn’t an issue since that bolt wasn’t used. Also note the LT4’s eight-bolt flexplate/flywheel crank flange pattern.
5. The first attempts at fitting this wet-sump LT4 resulted in multiple oil pan modifications as shown here. The Gen V oil pan is completely different than the Gen IV, so using one of those was a no go. Gillman had to replace the factory oil cooler with an aftermarket air-to-oil cooler mounted behind the front bumper.
6. Gillman is holding the factory oil cooler where it normally would be bolted to the engine. You can see that this clearly would not clear the Chevelle crossmember. This necessitated relocating the oil cooler to below the radiator.
7. Holley just released a GEN V LT1/LT4 cast-aluminum oil pan that they say will clear the crossmember and steering on early Chevelles and Camaros. The PN is 302-20. It includes a new pickup, windage tray, and fittings.
8. The LT1/LT4 engine accessory drives come without a power steering pump since the Corvette uses electric steering. This required Gillman to create a power steering mount and fit a Corvette pump using a pulley from a Chrysler product. Galpin may offer this mount as a separate part, that decision has yet to be made. But if you dig around online you can find others that do offer power steering solutions.
9. These two coolers were an early idea: one for engine oil and the second to cool the charge air. As you will see, this was later changed.
10. There just wasn’t room for the factory LT4 A/C compressor and relocating it proved troublesome, so GAS opted for an electric A/C pump offered by Sean Hyland Motorsports. Gillman placed the compressor and its controller in the area vacated by the battery. This compressor demands 30 amps continuous electrical current that the stock alternator can easily supply along with the other electrical demands.
11. The decision was made to retain the stock LT4 exhaust manifolds, which required extensive modifications to both sides. The driver side had to clear the steering column and the passenger side required re-directing the outlet inboard.
12. An earlier photo showed a pair of coolers: one for the supercharger intercooler and one for engine oil. The intercooler version was deemed too small. A larger charge air cooler was necessary that required it be placed between the radiator and A/C condenser. This created a serious packaging challenge because the engine was in a fixed position yet there had to be sufficient room to fit the required 4-inch inlet tube. This demanded hours of fabrication work to squeeze the cooler into place, including mods to the hood latch support bracket that appears stock—it is not.
13. When the intercooler was moved in front of the radiator and A/C condenser, this demanded new mounts that Gillman fabricated. The new mount is TIG welded to the bottom of the A/C condenser that mounts the intercooler radiator that is hidden.
14. Gillman laid out all the computers, controllers, wiring harnesses, and other pieces necessary to make the LT4 engine run. All these pieces had to find a home inside the engine compartment.
15. This shows all of the cardboard footprint templates that Gillman drew up on his way to the final configuration for placing all the electronic controllers on the firewall. The final arrangement is deceivingly simple yet it took multiple trials to create.
16. Here is the arrangement of the engine’s ECU, 4L80E trans controller, and the factory LT4 fuse box. The key to fitting everything was stepping the aluminum mounting plate off the firewall to allow running the massive wire package underneath the plate. Plus, Gillman reversed the cover on the GM trans controller so it would read correctly while exiting the wiring in the necessary direction.
17. The LT1 and LT4 engines use a separate pulse-width-modulated (PWM) fuel pump controller. There was not room for this unit with the engine ECU so Gillman moved it next to the master cylinder.
18. Gen V engines require a fuel delivery system capable of no less than 72 psi and 45 gallons per minute (gpm) of fuel delivered to the engine-mounted high-pressure pump. A good solution for fuel delivery would be an Aeromotive Phantom in-tank fuel pump conversion using the Stealth 340 pump. This pump is rated at 700 hp for forced induction EFI systems, but you might consider using a larger 450-lph pump that will cover up to 800 forced induction horsepower.
19. This final shot of the completed engine compartment may look like the swap was easy – it was not. Even the factory coil cover on the passenger side had to be trimmed to clear the ECU mount. It was that tight!
The Legacy of LT1
It’s a form of name-dropping. When someone mentions LT1 these days—the first question that has to be asked is “Which one?” Here is a quick history rerun on Chevrolet’s use of this Regular Production Option (RPO) code of LT1 and LT4.
All stories need to start at the beginning. The first LT1 option for Chevrolet engines was in 1970 in the Corvette. That was an 11:1 compression 350ci small-block Chevy making 370 hp at 6,000 and 380 lb-ft of torque at 4,000 rpm. The LT1 was also available in the Camaro, but devalued to 360 hp. The RPO LT1 lost much of its luster in ’71 at only 330 hp mainly due to a precipitous drop in compression. It also appeared in ’72 but at a paltry 255 hp rating. The LT1 was gone by ’73.
RPO LT1 returned to the Chevrolet roster in 1992 with the introduction of what Chevrolet called the Gen II small-block. This was an offshoot of the small-block with a cam-driven water pump, an optical-triggered distributor also driven off the front of the cam called Opti-Spark, and a reverse cooling system. The LT1 in the Corvette was rated at 300 hp and 330 lb-ft of torque and also powered Camaros and Firebirds and even in a lower horsepower application with iron heads in B-body cars! This was followed in ’96 with the LT4 that enjoyed larger intake ports, a more aggressive camshaft, and bigger valves. All this as the LT4 equaled 330 hp and 340 lb-ft of torque. These interim Gen II engines bowed out in 1997 with the introduction of the Gen III LS1.
Now we have the third generation of the LT1 and LT4—the first LT4 with a supercharger. With this latest generation engine, we’ve had to revert to a subscript to help differentiate the players. We call the earliest version the LT1A, the Gen II engines the LT1B and LT4B, and the latest version the LT1C and LT4C. It probably won’t catch on, but it does save time explaining which generation you’re talking about.
Getting to Know the LT4
Displacement: 6.2L, 376ci
Description: Gasoline Direct Injection (GDI), AFM, and VVT
Bore/Stroke: 4.065 x 3.622
HP: 650 hp at 6,400 rpm
Torque: 650 lb-ft at 3,800 rpm
Crankshaft: Forged 1528MV steel with forged aluminum balancer
Pistons: Forged aluminum, 10:1 compression
Connecting Rods: Powdered metal forged, 6.125 inches
Valve Sizes: Intake: 2.12/1.59 inch Intake/Exhaust
Supercharger: Eaton 1.7L four-lobe
Boost: 9.4 psi
Camshaft: Hydraulic roller, 189/223-deg. duration @ 0.050
Valve Lift: 0.492/0.551 inch Intake/Exhaust
Lubrication: Dry-sump or wet-sump
Injector Pressure: 2,900 psi
Engine Redline: 6,600 rpm
|LT1 GDI crate engine 460 hp, wet||19328728||Summit Racing|
|LT1 GDI crate engine 460 hp, dry||19329997||Summit Racing|
|LT4 supercharged crate, 650 hp, wet||19332621||Summit Racing|
|LT4 supercharged crate, 650 hp, dry||19332702||Summit Racing|
|LT1 electronics package||19303137||Summit Racing|
|LT4 electronics package||19331517||Summit Racing|
|LT1 accessory drive, GM, w A/C||19329990||Summit Racing|
|LT4 accessory drive, wet sump, GM||19332590||Summit Racing|
|LT4 accessory drive, dry sump, GM||19322614||Summit Racing|
|ICTBillet motor mounts||551363||ICT Billet|
|Holley retro-fit LT1 wet sump oil pan||302-20||Holley|
|Aeromotive Phantom 340 lph pump kit||18688||Summit Racing|
|Aeromotive Phantom 450 lph pump kit||18310||Summit Racing|
|The following chart lists only the major components along with a few aftermarket pieces that were mentioned in the story.|