When the LS engine was first introduced to the public, it didn’t take long for enthusiasts to make it the go-to engine for swapping into classic hot rods. Heck, even the Ford guys are using it. But, as great as the LS has proven to be, something better – at least in the eyes of Chevrolet – has come along. Enter the Gen V LT-series. This LS replacement is starting to make serious headway as the new modern-engine swap in the classic car world. The aftermarket is feverishly creating a catalog of parts to help you finish that switch to 21st-century performance.
Previously, we put together a two-part LS-Swap Guide to help you get that upgrade done. Now, we want to put together a list for the LT engine. Like the LS, there are a few items you need in order to swap an LT into an older vehicle. Unfortunately, very few swap parts from the LS platform will interchange to the LT.
Currently, the list of parts for an LT swap is limited, but we wholeheartedly expect the list to grow very quickly. The first-gen Camaro seems to be the focus right now, but we’re certain other models are soon to follow.
The Heart Of The Swap
While used LT engines are starting to take-up residence in many salvage yards, Chevrolet Performance LT-series crate engines are readily available from dealers. With horsepower ratings ranging from 455 to 650, there are a myriad of options. With a new engine having a retail starting cost just shy of $8,000, the budget-minded enthusiasts will probably venture to the salvage yard. If that is the case, what they will probably find most abundant are engines from GM pickup trucks.
Almost every 1/2-ton truck and SUV built since 2014, came with an L83 Gen V 5.3-liter engine that delivers 355 horsepower and 382 lb-ft of torque. The typical salvage yard L83 engine sells for about $1,500, depending on the year and mileage. One thing to remember, is the 2017-and-later Gen-V engines have a different ECM and harness. If you get just an engine, confirm what controller you need. As an aside, we have seen complete engine and transmission packages go for $6,000.
Although there are various differences between the LS and the LT engine, the engine mount embossments on the block are forward of the block center-line on both engines. This is different from the traditional Gen I small-block Chevy location. They also use a four-bolt pad.
There are several ways to mount the LT block to traditional small-block frame stands. The factory Gen-V mounts are different than traditional mounts. When bolting the engine to the frame, there are two types of adapters: sliding and static. While a static mount works for most applications, sometimes, you need a small amount of adjustability. That is when using a slider mount can be beneficial. In case you were wondering, a sliding mount is just as strong as a static mount.
Driving the accessories like the water pump, A/C compressor, and alternator on your new LT engine is a huge concern for enthusiasts. In most applications, the factory accessory-drive will not work. The LT engine’s water pump is offset (to the driver side on trucks, passenger side on cars), and the A/C compressor is mounted low and tight to the block.
Most aftermarket engine-mount adapters don’t clear the A/C compressor if it is in the stock location, and more-often-than-not, the compressor will hit the frame in most muscle cars. Also, LT-equipped vehicles possess electric power steering, and no power steering pump. There are several accessory drive kits available that include power steering.
While the LT crate engines can be had with both a wet or dry-sump oiling system, most enthusiasts will want to use the wet-sump system. Although the factory wet-sump oil pan is not overly large, it does have a front-sump which is really only suitable in truck applications. They just don’t fit GM muscle cars without modifying the engine crossmember. The swap to an LT engine requires using a new oil pan.
Headers are the most difficult part of completing an LT swap. Unlike a traditional small block, there are not many options available for swap headers. If you are concerned about forking out a bunch of money for what is available, the truck manifold does actually fit some GM A-body cars. The Corvette LT manifolds are a center-dump design, and don’t fit anything very well.
The Gen-V engine has a butt-load of sensors, and some, you probably will not need. If you grab an engine out of a truck, those engines have a belt-driven vacuum pump that is lubricated by the oiling system. When an LT engine is dropped into a muscle car, many times this pump is removed. That deletion requires the ports be plugged. GM has a kit (PN: 11546665) that takes care of this, or you can use an M12x1.75 plug with threadlocker.
Just like the LS engines, the LT’s crankshaft hub in the torque converter area requires an adapter when using an older GM automatic transmission. ICT Billet makes a really nice hub-adapter ring that drops into the crank to keep things in place and centered as it must be.
Since you’re swapping a modern engine into your hot rod, we’ll assume you are not planning to use a Turbo 350 or 400, and will be shifting one of GM’s latest electronic transmissions. The latest six and eight-speed automatics from GM are too large to install in a vintage car without cutting the body. For that reason, the 4L60-, 4L65-, and 4L75-series of four speed automatics are a great option.
The LT’s factory flexplate is designed for use with the latest six- and eight-speed transmissions. If you are swapping a 4LXX-series transmission, then you need a new flexplate like the billet SFI 29.2 unit from TCI (part No. 399860). The Gen V crankshaft is an 8-bolt.
If you plan to row your own gears by installing a manual transmission and are using an L83 truck engine, then you have a small problem. The crankshafts in the 6.2-liter car engines are machined to accept an input shaft from a manual transmission, but the L83 5.3-liter truck engines are not.
The fix is to space the transmission 3/8-inch back from the bellhousing. This can be accomplished with a spacer like the one from American Powertrain (PN: APGM-20001). You will also need to use the large (1.70-inch OD) 2010 Camaro pilot bearing, because the L83 crankshafts are not machined for the small inner bearing.
Unlike the many aftermarket EFI units that have a fuel-system return line, the LT runs a returnless, Pulse-Width Modulation (PWM) system that does not function with a return line. The PWM pump is controlled by a fuel module which handles all the work.
The Gen-V’s OE fuel system uses two fuel pumps, one in the tank and one under the intake. The mechanical pump under the intake runs off of the camshaft. Instead of using a traditional fuel pump and regulator, the factory pump is controlled by the ECM. This is done through a fuel-pump module that controls the fuel pressure as it reaches the mechanical Direct Injection fuel pump mounted under the intake. A pressure sensor located in the fuel line monitors the fuel pressure, which is maintained at 72 psi at 45 gph. The pressure is managed through the Pulse Width Modulation controlling the pump.
An easy fix for this is to use the Aeromotive Phantom Returnless pump system. It is PWM controllable, and can be installed into just about any stock fuel tank. Don’t try to use a regulated pump with a return line on a Gen-V LT engine. While the engine might run, you will have problems. If you don’t run the PWM system, the engine could be hard to start, won’t idle very well, and you will experience poor-running conditions, especially at WOT.
An engine harness can make or break a late-model engine swap. At one time, the only way to get a wire harness to connect the ECU to the engine, was to grab one from a salvage yard. But that entailed knowing how to re-pin the harness, and eliminate many unneeded wires. However, there are many aftermarket companies now making complete harnesses.
A late-model engine will not run without an ECM, and these control boxes are essentially the same for all Gen-V engines from 2014 through 2016. There were changes made in 2017. The simplest way to get around all of the wiring and tuning issues is to use the Chevrolet Performance LT-controller kit.
Since GM builds the ECM, they can do things no one else can. The factory Gen-V box typically does not have a tach output, but Chevrolet Performance does have a “retrofit” box for classic cars which has the required connection. It comes with all the sensors, harness, fuse box, ECM, and even a throttle pedal (which is another item you will need). By the time you purchase all that stuff individually, you could end up spending just as much – if not more – than buying the pieces separately. One thing to keep in mind, is the Gen V ECMs do not have a built-in transmission-controller. If you plan to use an electronically controlled transmission, a separate controller is a must have.
Finally, you will want to hook up the gauges, right? While you can install sensors for traditional gauges in the engine block, keep in mind, the threads in the block are not traditional SAE-pipe thread. That means adapters will be needed.
The Gen-V LT engine will be around for a long time, and quite possibly be the next big thing in engine swaps. Hopefully this short guide to some of the parts you’ll need can help you bring your classic into the modern age.