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Engine Swap: GM Gen IV L92 Makes Big Power

Posted in How To on August 1, 2012
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GM introduced the LS engine family of V-8 engines in 1997 in the Chevrolet Corvette as an all-aluminum engine, and the company has built upon this line ever since. These original versions, some with cast iron blocks and some with aluminum, were known as Generation III engines.

In 2005, GM introduced the Gen IV engines. The newer line brought larger bore sizes (for up to 7.0L displacement), different camshaft position sensor locations, and the addition of casting areas for GM’s Active Fuel Management cylinder deactivation methodology.

We got news that the guys at Crocker Off Road Performance in Phoenix, Arizona, were doing a unique GM swap into a ’98 Jeep TJ owned by John James from Cottonwood, Arizona. What stands out is their use of a 400-plus-hp Gen IV L92 engine transplanted from a Cadillac Escalade. The L92 is a 6.2L Vortec engine used in the Escalade and several other GM SUVs and trucks. It boasts an all-aluminum design with traditional pushrod technology, but utilizes variable valve timing. It was rated from the factory at 403 hp and 415 lb-ft of torque.

To make things ever more interesting, John backed this potent powerplant with a 6L80 six-speed automatic with full automatic and manual shifting options. When all was done, the Crocker guys made this engine look like it belonged under the hood from day one.

Going forward, the Gen IV engines will be a popular powerplant option for those wishing to swap in a modern engine with the latest technology. This class of motors offers improved fuel economy, efficiency, horsepower, and smooth drivability. Here’s a quick rundown of things to consider when swapping any non-stock engine into your rig, and also some details specific to how you can put GM Gen IV technology under your hood.

01.Typical late-model engines have eliminated the ignition distributor completely and use one coil per cylinder. The L92 has four coil units mounted atop each of the valve covers. Using a dedicated coil per cylinder allows the manufacturer to precisely fire each coil and spark plug as needed. The engine computer can adjust the ignition timing for each individual cylinder, improving both power and fuel economy.

02.You’re staring down the throat of a 90mm throttle body for this 6.2L V-8. To the throttle body, the shop crew added a custom intake boot and filter to fit the available area under the hood.

Fuel pressure to the injectors for the L92 should be about 58 psi, so a healthy pump that can move good volume is needed to keep this engine happy. A Bosch 040 in-tank pump was mated onto a 2005 Jeep TJ fuel pump sender and dropped into an aftermarket fuel tank for this particular build. A C6 Corvette regulator was used downstream.

03. Setting an engine such as this between the frame rails depends on just how much room you have in the engine compartment. Crocker used a set of M.O.R.E. engine mounts in this case. Depending on your particular swap and recipient vehicle, you may have to build custom mounts, or aftermarket pieces might be available. When doing an engine swap with new mounts, it’s vital to make sure the engine, transmission, and T-case mounts are compatible. That is to say, you don’t want one end mounted solidly while the other end sits on soft rubber mounts. Mounting point failure is likely to follow in this scenario.

04. Crocker ordered a custom built Ron Davis aluminum radiator with integrated transmission cooler to fit within the confines behind the grille. The water outlets were positioned to best align with the outlets on the engine. Sometimes, it’s possible to find a formed hose to fit a conversion, but often a universal flex hose will offer the smoothest fit, as was done here.

This engine came with a typical factory mechanical fan, but it was removed in favor of using a single large diameter SPAL electric fan behind the radiator. The Ron Davis radiator/fan/shroud assembly was custom built based on the rated engine HP and operating altitude for the vehicle. The cooling system is not the place to skimp when dropping in a high-horsepower engine.

05. We’ve seen some engines with rather odd radiator and heater hose configurations, but the L92 is pretty straight forward. There are, of course, radiator inlet and outlet tubes. There is also a pair of tubes for the heater system. The factory aluminum water neck of an L92 is aimed towards the passenger fender. Crocker cut, rotated and TIGwelded it to a more forward position aimed at the radiator.

06. Mating air conditioning components can get a little tricky, but if you live in a hot climate it’s nice to retain this comfort feature through an engine conversion. You need to route the A/C compressor wire to the new compressor and have custom hoses built or adapt the two sets of factory hoses to mate the compressor to the vehicle system. When mating to an older R-12 refrigerant system, it may be necessary to change out some of the old A/C components to be compatible with the newer R134A refrigerant.

07. Most starter hookups are pretty straightforward and swap directly. In some cases, it may be necessary to add a relay between the ignition switch lead and the starter solenoid to provide sufficient current to energize the solenoid. Also, be mindful of the need for ground straps from the engine to frame or transmission to frame.

08. Like most all engines built today, the L92 uses a serpentine belt to drive the water pump and all accessories. This makes standard belt setup a snap, but can make it more difficult if you ever decide to add other belt driven pumps to the engine.

09. When dropping a V-8 in an engine compartment with limited room between the frame rails, close fitting factory cast manifolds may offer the best exhaust solution. In the case of the L92, C6 manifolds fit close and offer good flow into 2.5-inch tubes on both sides. They also dump to the rear of the engine, behind the motor mounts. Block hugger headers can be used as well in tight spaces. Bulky factory cast manifold flanges may interfere with the frame rails in some cases.

10. With space at a premium, Magnaflow bullet cats were tucked just inside the frame rails and alongside the T-case, a Magnaflow 2.5-inch muffler continues the exhaust system. For most engine swaps, the exhaust is one of the last items on the checklist. Space under the body and between the frame rail will dictate what system you can accommodate and a skilled exhaust installer may be prized to finish the job.

11. The scariest part of swapping in newer engines for most people tends to be the wiring harness portion of the project. If you’re not comfortable splitting harnesses and assembling what you need, it may be a very good idea to partner early in the project with an experienced tuner to modify your harness and program your ECM for your specific application. For this swap, John Spear at Speartech Fuel Injection Services built a new harness for this application. John is an ex-GM electrical engineer and well knows his way around these engine control systems. Here the reprogrammed E38 computer sits in the footwell.

12. The transmission used in this swap is the GM 6L80 six-speed automatic. This transmission is best used with a Gen IV reluctor engine controlled by an E38 computer. The 6L80 electronic transmission control module must be pulled from the tranny and delivered to the tuner to be reprogrammed for the vehicle swap.

13. The tail of the 4WD 6L80 has the same bolt pattern as the very common 4L80 transmission, so mating up a transfer case means you have several options. In this case, John chose to go with a 3.0:1 Atlas transfer case, which bolted right up.

14. Here’s a snail’s eye view the bottom of the drivetrain. The L92 comes with a deep aluminum pan with rear sump. Behind that you can see the aluminum transmission bellhousing and the deep fluid pan for the auto. Crocker used a set of factory transmission hard lines that fit under the tranny and engine perfectly. Where the lines emerged under the radiator, the crew cut the lines and then spliced to soft lines routed to the cooler in the radiator assembly.

15. When it came time to hook up the transmission shifter, Crocker installed one taken from a 2011 Chevy Malibu. It can shift normally to Park, Reverse, and Drive. But, it can also go into manual mode allowing the driver to tap shift up and down through the gears with a button on the side of the shifter knob. Very slick!

16. Auto Meter gauges were skillfully adapted into the dash of the Jeep and were wired and plumbed to the engine to provide vehicle vital signs.

17. Add a big motor and you’ll need to consider how much strength you have in the rest of the drivetrain. In this case, John opted to upgrade the rear axle to a Currie-built Dana 60.

He originally had 4.10 gearing but swapped down to 3.73 gearing. While the lower gearing (higher numerically) may seem like a great fit with the 33-inch tires John is running, a motor with this much horsepower and torque on a light vehicle is much better behaved with the 3.73 gears.

18. With the swap complete, this rig scoots with about 450 hp (with the retune). It has the smooth power of a modern engine and a six-speed tranny with tap shifting at the owner’s finger tips.


Crocker Off Road Performance
Speartech Fuel Injection

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