The LS engine has been around for 24 years now, and it doesn’t look like it’s going away anytime soon as the go-to swap option for classic cars and trucks. This power plant has shown its versatility and performance potential over the years, making it an easy choice for performance enthusiasts that want modern driveability out of their hotrods. However, since GM has introduced the LT engine in its newer vehicles, we now have another option for an up-to-date engine swap. The only question is, is the LT a better platform than the LS?
In the video, Auto Guild does an excellent job of talking about all of the differences between the two powerplants, and there are a lot. As most of you know, the LT’s direct injection is much different from the LS’s fuel system, but that’s not all. The only thing that these two platforms have in common is five parts, the starter bolts, wrist pins, and a few other bolts used in the assembly. The LT front and rear covers, valley cover, valve covers, and oil pan are entirely different from the LS, and the differences don’t stop there.
When GM designed the new LT platform, they basically started with a blank sheet of paper. They did keep the traditional single camshaft, which dates back to the early days of long ago. And while direct injection (DI) is new for this platform, there are many other changes as well.
The LT blocks are all-aluminum, and the only way to find an iron block is to find the 6.6-liter engine out of GM’s HD truck lineup. Block strength is also different. Auto Guild states that the LS aluminum engines can hold 700 horsepower while the iron engines can take 1,000. The LT blocks are more robust in design than the LS, thanks to its gusseted water jackets. This is one reason why the LT aluminum block can take up to 900 horsepower, and the L8T iron block should be safe in the 1,200 horsepower range.
Unlike the LS, the LT has eight oil sprayers that spray the pistons’ bottoms, which allows for a cooler combustion process, higher compression, reduced friction, which equates to more power. The LT also offers forged rods with a better design that connects to a forged steel crankshaft. GM also addressed the windage problem that the LS had and reduced the situation in the LT.
Head and Valvetrain
As you can imagine, due to direct injection, the cylinder heads have been redesigned as well. GM also flipped the intake and exhaust valves when compared to the LS. This change improves cylinder head flow and puts the spark plugs in a better location for enhanced combustion, making the engine more efficient. GM also increased the head bolts from 11mm on the LS to 12mm on the LT. The rocker ratio was also modified, going from 1.7 to 1.8. The engineers also decided to use a significantly larger camshaft in the LT, producing smoother valve action, which offers less stress on the valvetrain.
Variable Valvetrain (VVT)
Some of the LS engines offered variable valve train (VVT), but the LT is new and improved. With the LS, the VVT was either on or off. With the LT, it’s always working and making changes to the timing to optimize the unit’s performance. These adjustments allow the Gen 5 engine to make massive torque amounts while still making good horsepower at high RPM. The new cam phaser can adjust the angle of the camshaft 62-degrees, which is impressive compared to the LS’s adjustment of only 20-degrees.
Other changes for the LS platform include dynamic fuel management (DFM), active fuel management (AFM), new exhaust manifolds, 2.9-million lines of code operating the engine, new intake manifold, dual-stage oil pump for increased power, positive crankcase ventilation, 87mm throttle body, air induction humidity sensor, and an integrated stop-start system. Even though the LT has many improvements in its design, unlike the LS, it’s not flex-fuel capable from the factory.
While the LT has several advantages over the LS, it does have its downfalls as well. The LS has the full support of the aftermarket, is still inexpensive to purchase, and can be adapted to any vehicle pretty easily. The LT engines are expensive, less aftermarket support, and more challenging to install in an older car due to direct injection and the lack of a power steering pump. However, no matter which platform you choose, you will still be miles ahead in technology when compared to the Gen I and Gen II small-block Chevys.