What LS Blocks Are Aluminum?

By Chris Thatcher

Updated Feb 18, 2024

In Learn Feb, 2024

The LS engine platform is one of the most popular and frequently encountered in GM circles. Not only has the entire LS engine platform remained popular since it debuted in 1997, but there were so many produced that they are still super-common and can be found at just about any parts yard for a reasonable cost. Here we will cover what LS blocks are aluminum?

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    Where We Buy
    We highly recommend using eBay as it provides a secure platform, ensuring protection against scams.
    If you're looking for a used LS Engine to buy, honestly, we buy from eBay. I cannot tell you how many times I have bought a junkyard LS from a local "reputable" Junkyard and got screwed with a bad motor and then they wouldn't warranty it. I buy from Ebay because typically the vendor is more accountable because they don't want bad reviews, they also provide a decent warranty, and worst case, Ebay and Paypal can get involved if necessary.

    The LS engines are easy to build, and simple to work on and customize yourself. On top of that, there are countless companies that sell the LS engine and aftermarket parts.

    The only thing you need to know before you get that nice new block is exactly what LS engine blocks are made of aluminum, and we’ve got the answer for you.

    What LS Blocks Are Aluminum

    Aluminum Block: The Short Answer

    The LS blocks were made in both iron and aluminum for nearly every size, however, the aluminum blocks were produced in generations 3 and 4 of the LS engine platform. Gen III was simply a starting place for truck engines, LS engines, and more.

    They were most frequently used in cars while the iron block engines were put mostly in trucks. While this isn’t the rule across the board, it does hold true most of the time. LS based engines offered active fuel management among other LS engine benefits.

    What Is The Difference In Each Aluminum Block?

    There were a lot of different aluminum block types used during the 3rd and 4th generations, and just about every engine that went into production had both a cast iron and an aluminum counterpart.

    Generation III (Gen III)

    Gen III 5.7L (LS1 & LS6)

    The 5.7L gen III LS engine blocks made from 1997 to 2005 (gen III block) were both 3.90-inch bore (a larger bore) blocks, with a stroke of 3.62 and compression ratios of at least 10.25:1. The LS1 produced 300-350 hp @ 5,600 rpm, while the LS6 produced 385-405 at 6,000 revs. The first LS engine started out impressive.

    Gen III 5.3L (L33 & LM4)

    The L33 gen III was produced from 2005 to 2008 and had 3.78-inch cylinder bores with the same 3.62-inch stroke as the 5.7L blocks. The L33 gen III was capable of putting out 310 hp at just over 5,000 rpm. The LM4 produced 290 HP with identical measurements. Think about truck engines here.

    L33 LS engine

    Generation IV (Gen IV)

    Gen IV 5.3L (LH6, LH8, L9H, LC9, LS4)

    With 3.78-inch bores, the 5.3L LS engines (Gen IV) have respectable power outputs of 300-315 hp for the LH6, 300 for the LH8, 403 hp for the L9H, 315 hp for the LC9, and 303 for the LS4. These engines were largely produced from the late 2000s to the early twenty-teens.

    Gen IV 6.0L (LS2, LS3, L76, L98, LFA, LZ1)

    The 6.0L LS engine blocks from gen IV are generally much higher output than the previous generation. The LS2 puts out 390-400 hp with a 4.00 large bore and 3.62 stroke. The LS3 puts out more than 430 hp, the L76 creates 360 hp, the L98 makes 362 hp, the LFA makes 332, and the LZ1 creates 332 hp.

    Ls3 engine

    Gen IV 7.0L (LS7)

    One of the most incredible LS engine block models for Chevrolet performance LS , the LS7 from Gen IV creates a monstrous 505 hp @ 6,300 rpm as a bone stock engine. It has a 4.125 inch bore, a stroke of 4.00, and features an 11:1 compression ratio. This engine is so powerful, a variation of it is used in a Le Mans Series car. Gen IV stands apart here.

    Truck engines can really improve with a tall deck and aluminum cylinder heads.

    Why Is Aluminum Block So Desirable For LS Engines?

    The primary reason that people love aluminum version LS engines is the power that can be created with a lightweight block on a standard deck. Since the cylinder heads are significantly lighter than cast iron blocks they can be used in a number of different applications where large iron engines would be prohibitive.

    One of the most popular applications is performance daily driving or track use. Active fuel management is a priority. It is the epitome of Chevrolet performance. With forced induction and variable valve training, you get far better delivery.

    What Other Options For Blocks Are There?

    While aluminum blocks may offer the greatest power potential for the weight, there are other block material options out there. Cast iron and various magnesium alloys are the other two encountered most frequently.

    Iron Block

    For most of the last century, engine blocks were largely made from iron, and this is still the standard in many cases when it comes to high-output engines or other applications featuring hard use that requires a stronger block.

    While an iron block is very strong and the metal can be far cheaper than specialized alloys, they are also incredibly heavy. Paired with spun cast iron liner, when compared to LS engines, you simply can't win here.

    The weight of the iron engine block factors into the power vs. weight consideration heavily. This can affect not only track times but also simple drivability, which is why many people look for aluminum LS engine blocks.

    For a time, they even tried iron sleeves for the benefit of cast iron without so much weight.

    Magnesium Alloy Block

    While not generally common knowledge, several auto manufacturers have produced engine blocks made from various magnesium alloys. The benefit to these is a decreased weight from iron, as well as an increased hardness.

    Manufacturers such as Mercedes-Benz, Jaguar, Fiat, Ford, Audi, and even Kia have at one time or another produced a vehicle with a magnesium-based engine block.

    One of the problems that eventually lead to discontinuation of this is the difficulty of working with magnesium, which is highly exothermic when it comes into contact with water. This deep skirted block casting simply had too many risks.

    LS Engine Aluminum Blocks

    As you can see there are so many aluminum blocks to choose from, in various bore sizes and displacements, for just about any project you can dream up. There are relatively smaller 5.3-liter LS engine blocks that can give you 300-400 horsepower at the turn of a key, and there are 6.0L and 7.0L powerhouses that can really tear up the road when you use them in the right build.

    The choice is yours, and if you are looking for aluminum LS engine blocks for your engine build, you really can’t go wrong.