It was 1955 when Chevy engineers unveiled the “small block” V8. Clearly, they knew what they were doing because it’s still going strong. Of course, there have been some changes over the years, and Chevy’s parent, GM, defines these by “generation.” Thus, there’s a Gen I, a Gen II and so on, up to the relatively recent Gen V.
Each design or version of the small block also receives a two-letter designation. For the all-aluminum Gen III and IV engines, these two letters were “LS.” That’s why every aluminum small block V8 of that era is an LS something. Keeping things simple, we enthusiasts call these the LSx engines. (There are iron block versions. They go under the Vortec name.)
If you’re considering installing an LSx crate engine, it’s important to understand the differences between the versions.
Gen IIILS Engines
The LS1 appeared in 1997 under the hood of the C5 Corvette. Displacing 5.7 liters (345ci), this is clearly a direct descendant of the ’55 motor, because it uses the same bore center distance (4.40 inches). (Interestingly though, the firing order was changed from the Gen II.)
A more powerful version of the LS1, dubbed the LS6, appeared in the Z06 ’vette in 1999. This has a modified block casting plus unique cylinder heads, intake manifold and camshaft. The LS1 was phased out in 2004 and the LS6 disappeared in 2005, to be replaced by the Gen IV small block.
Gen IV LS Engines
The Gen IV engine has much in common with the Gen III. Both have six-bolt main bearing caps and a center main thrust bearing. They use a four-bolts-per-cylinder head pattern, have lifter bores of a .842-inch diameter, and were designed for coils at the plugs rather than a distributor ignition (and yes, bore centers are still 4.40 inches). However, there are also some significant differences.
Gen IV engines use a 58-tooth reluctor wheel for more precise ignition timing, rather than the Gen III’s 24-tooth wheel. In addition, the Gen IV was designed for GM’s cylinder activation technology, christened Active Fuel Management (AFM). Last, Gen IVs gained variable valve timing (VVT).
The first Gen IV LS engine to appear was the LS2 in 2005. This had bigger bores than the Gen II, upping capacity to 6 liters (364ci.) Also that year, GM brought out the LS4. This was a 5.3 liter modified for use in FWD vehicles.
In 2006 the LS7 arrived, boasting bigger bores and a longer stroke that together created 7 liters (427ci) of displacement. To reduce mass and handle the additional loads, the connecting rods were made from titanium.
If you were expecting the LS numbers to follow a logical progression, think again, because in 2008 along came the LS3. With bores larger than those on the LS2, this had 6.2 liters or 376ci of displacement and a stronger block casting to handle the additional power.
The LS3 begat the LS9, the LSA and the L99. Starting with the LS9, this was a supercharged version of the LS3. The LSA was also supercharged, but to a lesser extent, allowing it to be used in the Cadillac CTS-V.
The L99 was essentially an LS3 configured for use with an automatic transmission. Thus, it came with AFM and VVT. This was produced until the 2015 model year, while the LS3 continued until 2017.
Before the LS3 and L99 were phased out, a new engine had already arrived. Designated the LT1, this was the fifth generation of the now-legendary small block V8. It just keeps on going.