LS or old school 350? This is a debate that will likely never have a definitive outcome. LS engine swaps have truly reached critical mass. The swap is easy, and the amount of aftermarket support is astounding. The cost of working over a “recycled” LS-style engine compared to the cost of rebuilding a worn-out old school 350 short-block is becoming quite competitive, even if you consider the additional costs of adapting the late-model engine to an early chassis. And, since the typical rebuild of an LS is achieving roughly 100 more horsepower compared to similarly modified, equivalent-displacement, traditional Chevy small-block, it’s tough to argue with the LS’ capabilities.
Let’s first look at building your classic small block. For starters, if a production 400 block is already .030-inch over, consider it used up. You might be able to get away with .040-inch overbore if it is an engine for street use, but if you’re planning on racing, you’re asking for trouble with a cylinder wall that is machined this large with a Siamese-bore block. For the sake of argument, let’s say the block does in fact clean up at .040-inch over. The cost to do the required machine work to the block (i.e. machining, hot-tank, MAG inspection, squaring the decks, bore and hone the cylinders with a deck plate, align-hone the main and cam bearing bores, turn the crankshaft, etc, etc.), can run around an $800 to $1,000. The short 5.565-inch connecting rods will, at a minimum, need to be shot-peened, MAG-inspected, rebuilt, and fitted with ARP bolts. After you have paid for all of that work, you still have a less-than-optimal 1.48:1 rod/stroke ratio that results in excessive thrust loads on the cylinder walls. For that reason, you should plan to use a set of 5.7—or preferably, 6.0-inch aftermarket rods, custom-forged pistons, and rings. Do you see the costs adding up? We haven’t even started to add the costs of rebuilding a set of heads that flow nowhere near as well as a set of LS heads. If you are being conservative, and planning on around 450 horsepower, you’re still looking at a cash outlay in the $3,500 to $4,000 range for a short block.
We saw a recent test of a 5.3-liter engine that was removed from a wrecked truck with slightly over 60,000 miles make 340 horsepower with the stock cam, and 1-3/4-inch headers with a carburetor. While not as plentiful, the larger 6.0-liter LS engine is more than capable of making 500 to 550 horsepower with decent heads, the right cam, intake, and exhaust. It is initially more expensive when leaving the salvage yard, but if you can afford the bigger engine, its power and torque peaks should occur at a much more user-friendly rpm than that of the 5.3-liter. The 6.0-liter also has a 4-inch bore.
The days of buying a used small block from a salvage yard for $1.00 a cubic inch are long gone. Heck, just finding a pre-LS small block in a salvage yard is nearly impossible. So, there is another reason to consider the LS engine. But, what does a used LS engine go for? We did a little Inter web searching, and found several places that sell 5.3-liter take-out engines for between $800 and $1,600. If you make the jump to a 6.0-liter, you can plan to spend around $1,500 – $2,000, and some of them even came with the wire harness and controller! Having the controller is great if you intend to keep the fuel injection, and why wouldn’t you?! To top it off, these engines can be installed “as-is”, and run.
As performance technology improves, we are continuously learning better ways of doing things with better results. The LS is the pinnacle of that improved technology, because it delivers easier, cheaper horsepower than the classic small block, with the dependability and tuning capabilities of fuel injection. The block architecture of the LS series makes for an extremely strong engine. The aluminum LS engine blocks are nearly as strong as the Gen 1 and Gen II cast iron blocks. The iron LS engines that are found in trucks far exceed the capabilities of the previous two generations.
The cylinder heads of the LS engine gives it a huge advantage over the classic small block. While the classic small block Chevy uses heads with the valves at a 23-degree angle, the LS valves are positioned at 15-degrees. What this means, is that with large bore and short stroke, the LS engine can make more power. What the different angles equate to is a straighter path from the intake to the cylinders, resulting in more port velocity. The heads are also capable of supporting larger valves than the previous classic heads. While Brodix and others make heads for classic engines with better valve angles than stock, simply buying them is an added cost of building the classic small block.
The LS engine also used a coil-near-plug ignition to replace the distributor setup of all previous small-block engines. From a performance standpoint, having a separate coil for each cylinder gives each coil more time to recharge between cylinder firings. With single coil distributor systems, the coil must supply a spark, or fire, four times with every revolution of the crankshaft in a V-8 engine. With a multi-coil system, each coil only has to fire once every other revolution of the crankshaft. This provides more saturation time for a hotter spark, especially at higher rpm when firing times are greatly reduced. The result is fewer misfires, a cleaner combustion, and better fuel economy. Having a separate coil for each cylinder also improves the engine’s ability to handle more exhaust gas re-circulation, which helps reduce emissions. A hotter spark also makes spark plugs more resistant to fouling. Finally, a multi-coil ignition system also improves idle stability and idle emissions as well.
There is a lot interchangeability between all LS engine parts, including those between Gen III and Gen IV versions. Cylinder heads, crankshafts, intake manifolds and more can be mixed and matched, but there are some details to watch. Not every head matches every intake manifold, and not every crankshaft works with every engine combination. There is a book by Will Handzel, “How to Build High-Performance Chevy LS1/LS6 V-8s” – P/N 88958786. This is a great reference that outlines the more specific differences and interchangeability among Gen III-based engines.
When it comes to intakes, the aftermarket support of the LS engine is vast. Let’s say that you want to retain the fuel injection, you can stick with the factory intake, or upgrade to an intake from makers like Holley or FAST. If you still like the old-school feel of a carburetor, Edelbrock and Holley can support your need.
So there are some basics about why an LS engine should be a consideration for your next project. So what are you waiting for, get that LS, you know you want one. Below is a breakdown of all the engine variations:
LS1/LS6 LS1 5.7-liter engines were produced between 1997 and in the US (Corvette, Camaro, Firebird and GTO). The LS6 was introduced in 2001 in the Corvette Z06, and was built through 2005, where it also was found in the first generation of the Cadillac CTS-V. The LS1 and LS6 share a 5.7-liter displacement, but the LS6 production engine uses a unique block casting with enhanced strength, and other minor differences. The heads, intake manifolds and camshaft also are unique to the LS6.
LS2 In 2005, the LS2 6.0-liter engine and the Gen IV design changes debuted. Its larger displacement brought greater power. The LS2 is one of the most adaptable engines, as LS1, LS6, LS3 and L92 cylinder heads work well on it.
LS3/L99 Introduced in the 2008 Corvette, the LS3 brought LS base performance to an unprecedented level: 430 horsepower from 6.2-liter, making it the most powerful base Corvette engine in history. The LS3 block not only has larger bores than the LS2, but a strengthened casting to support more powerful engines, including the LS9 supercharged engine.
LS4 Perhaps the most unique application of the LS engine in a car, the LS4 is a 5.3-liter version used in the front-wheel-drive Chevrolet Impala SS and Pontiac Grand Prix GXP. The LS4 has an aluminum block and unique, low-profile front-end accessory system, including a “flattened” water pump, to accommodate the transverse mounting position within the Impala and Grand Prix. It is rated at 303 horsepower and 323 lb-ft of torque.
LS7 The LS7 and its 7.0-liter displacement makes it the largest LS engine offered in a production car. Unlike LS1/LS6, LS2 and LS3 engines, the LS7 uses a Siamese-bore cylinder block design which was required for its 4.125-inch bores. Competition-proven heads and lightweight components, such as titanium rods and intake valves, make the LS7 a street-tuned racing engine, with 505 horsepower.
LS9 The LS9 is the 6.2-liter engine that is supercharged. It is rated at 638 horsepower. The LS9 uses the strengthened 6.2-liter block with stronger, roto-cast cylinder heads and a sixth-generation 2.3-liter supercharger. Like the LS7, it uses a dry-sump oiling system.
Gen III and Gen IV Truck Engines Although performance car engines have typically carried “LS” designations, truck engines built on this platform are called Vortec. Truck engines were distinguished by iron blocks, and were offered in smaller displacements than car engines.
Here’s a quick rundown of the previous and current-production LS truck engines: 4.8-liter: The smallest-displacement LS engine (293 cubic inches); it uses an iron block with 3.78-inch bores and aluminum heads.
5.3-liter: The most common LS truck engine (327 cubic inches), it uses the same iron block with 3.78-inch bores as the 4.8-liter, but with a longer stroke, (3.62-inch) crankshaft. There are both iron and aluminum cylinder blocks.
6.0-liter: Used primarily in 3/4-ton and 1-ton trucks, the 6.0-liter (364 cubic inches) uses an iron block (LY6) or aluminum block (L76) and aluminum heads.
6.2-liter: Commonly referred to by its L92 engine code, the 6.2-liter (376 cubic inches) engine uses an aluminum block and heads, and incorporates advanced technology including variable valve timing. The L92 is used primarily as a high-performance engine for the Cadillac Escalade and GMC Yukon Denali.