Stroking An Ls1: Is It Possible And Worth It?

The LS1 is a small-block V8 engine designed and manufactured by General Motors. Introduced in 1997, the LS1 was the progenitor of the new architecture design that would transform the entire V8 line and influence the last of the big-block engines. The LS1 was first fitted in the Chevrolet Corvette and has powered every generation of the Corvette since. The LS1 is an all-aluminum 5,665 cc (5.7 L; 345.7 cu in) pushrod engine with a bore and stroke of 99 mm × 92 mm (3.898 in × 3.622 in).

The LS1 can be stroked, and there are a few ways to go about it. Stroker kits are available in the market, which include the crankshaft, rods, pistons, rings, and bearings in convenient pre-bundled packages. The crankshaft is the heart of a stroker, and in the LS1, the factory uses a 3.622-inch crankshaft. For a stroker, one can go with a 4-inch stroke, giving a total of 383 cubic inches (6.3 liters). This would require minimal clearancing of the engine block to fit.

Another way to increase the displacement of an internal combustion engine is to increase the cylinder bore. However, there is a minimum thickness that must be kept in the LS1's stock cast iron cylinder liners, and there isn't a whole lot of room to work with. The maximum overbore is generally accepted to be 10 thousandths of an inch.

The LS1 has been a popular choice for engine swaps in the car enthusiast and hot rodding community due to its serviceability and parts availability.

LS1 stroke and bore

The LS1 is the original Gen. 3 small block engine from General Motors, used in cars from 1997 to 2004. The bore and stroke of your stock Chevy LS engine are critical to know when rebuilding or upgrading your GM LS motor.

The LS1 engine has a 3.622-inch crankshaft from the factory, but you can increase the crankshaft stroke to make a stroker engine. This will increase the displacement and the cubes. Stroker engines are common upgrades for LS1 engines, and there are two ways to do this: increase the cylinder bore or increase the crankshaft stroke.

To increase the bore, you would need to increase the diameter of the piston, which would increase the diameter of the cylinder. However, there are limits to how much you can bore out an LS1 engine. The maximum overbore is generally accepted to be 0.010 inches, and re-sleeving the engine with larger cylinder liners is expensive.

Increasing the crankshaft stroke is a more popular option for LS1 engines since there is more room to work with. This can be done by swapping out the crankshaft for one with a longer stroke. The LS1's stock 3.622-inch stroke can be increased to a 4.0-inch stroke, for example, which would give you a 383-cube LS-wonder. This longer stroke will increase the cubes without requiring extensive clearancing of the block.

When increasing the stroke, you will also need to change the other components of the rotating assembly, including the pistons and connecting rods. The piston still needs to reach the top of the bore during each crankshaft revolution, so the stock LS1 pistons' pin location would require a shorter rod if used with a longer-stroke crank. Additionally, the stock powdered metal steel connecting rods are press-fit to the piston pins, and most aftermarket cranks have filleted edges that are not compatible with the stock rods. Therefore, it is recommended to buy an entire rotating assembly that is already matched and balanced.

When increasing the stroke of an LS1 engine, you will also need to check the clearances between the rotating assembly and the block to ensure there is no interference. The increased stroke will push the crank journals and connecting rods further outward, so you will need to temporarily assemble the crank to the block with oil in the bearings and spin it to check for any areas of interference.

In conclusion, increasing the stroke of an LS1 engine is a common upgrade that can be done by swapping out the crankshaft and other components of the rotating assembly. This will increase the displacement and cubes of the engine, resulting in more power. However, it is important to carefully select and match all the components and ensure that there is no interference between the rotating assembly and the block.

LS1 crankshaft

The LS1 is the original Gen. 3 small-block engine from General Motors, used in cars from 1997-2004. The crankshaft is a vital component of the LS1 engine, and there are a few things to consider when choosing the right crankshaft for your LS1 stroker build.

Firstly, the stroke of the crankshaft determines the distance the pistons travel in the cylinders, which ultimately affects the engine's displacement. The factory LS1 crankshaft has a stroke of 3.622 inches. For a stroker build, you can choose a longer stroke crankshaft to increase the engine's displacement and create more power. Common stroker crankshafts for the LS1 have strokes of 3.900 inches, 3.903 inches, or 4.000 inches, resulting in displacements of 383 cubic inches or more.

Secondly, the material and construction of the crankshaft are important factors. Forged 4340 steel crankshafts are commonly used in LS1 stroker builds due to their strength and durability. The LS1 crankshaft is typically made from forged 4340 steel, which can handle the increased stress and horsepower of a stroker engine.

Additionally, the counterweights and journal design of the crankshaft can impact its performance. Some crankshafts feature filleted edges around the journals, which require matching connecting rods. The counterweights help balance the rotating assembly, and their design can vary depending on the manufacturer.

When selecting a crankshaft for your LS1 stroker build, it is crucial to consider the compatibility with other components, such as the connecting rods and pistons. Choosing a matched rotating assembly kit can simplify the process and ensure all the components work together optimally.

In conclusion, building an LS1 stroker engine requires careful consideration of the crankshaft as it plays a vital role in achieving the desired displacement and performance. By selecting the appropriate stroke, material, and design, you can create a reliable and powerful LS1 stroker engine.

LS1 piston and connecting rod installation

Step 1: Crankshaft Installation

The crankshaft is a heavy component, so handle it with care and consider getting assistance. Before installing, wipe the crank main journals with mineral spirits. Then, gently lay the crankshaft into the block, being cautious not to scratch the highly polished journals.

Step 2: Connecting Rod and Piston Preparation

Disassemble the connecting rods and attach them to the pistons. Install the piston rings and clock them onto the pistons following the manufacturer's recommendations. Lunati, for example, specifies a minimum piston ring end gap of 0.004 inches per inch of cylinder bore diameter for the top ring.

Step 3: Piston and Connecting Rod Installation

Coat the cylinder wall with WD-40 for lubrication. Carefully guide the piston and rod assembly down the cylinder bore, using one hand to lower the piston while the other guides the rod onto the crank journal. Ensure the chamfered side of the rod faces the filleted edge of the crank journal.

Step 4: Connecting Rod Tightening

Tighten the rod caps following the manufacturer's torque specifications and sequence. Lunati, for instance, uses rod bolt stretch measurement to ensure accurate bolt preload. This method directly measures the elastic deformation of the bolt, providing a direct indication of the clamping force.

Step 5: Final Assembly

Refer to the GM service manual for your vehicle to complete the final assembly process. This will include reinstalling any block plugs and following the recommended torque sequence for securing the main bearing caps and other components.

Tips and Tricks:

• Always use high-quality tools and components from reputable manufacturers.
• Inform yourself about the process beforehand and set realistic goals.
• Clean the engine block and components thoroughly before assembly.
• Check bearing clearances to ensure they are within the proper tolerance to avoid reduced bearing life.
• Use Plastigage to measure bearing clearances by squeezing it between the bearing and crankshaft journal.
• Follow the manufacturer's recommendations for piston ring end gaps to avoid power loss or engine damage.
• Label and mark the connecting rods and pistons during disassembly to ensure proper reassembly.

By following these steps and tips, you can successfully install the pistons and connecting rods in your LS1 engine, ensuring reliable performance for many miles to come.

LS1 engine block machining

The LS1 is the original Gen III small-block engine from General Motors, introduced in the 1997 Chevrolet Corvette. The LS1 engine is known for its lightweight aluminium block loaded with groundbreaking features. The LS1 block is quite different from previous small-block designs, with internal parts designed to "find their own home", simplifying the machining process and eliminating the need for dowels. The LS1 block features extra-long torque-to-yield head bolts, a deep-skirted bottom end, and a raised camshaft. The LS1 block is also lighter, smaller, more rigid, and more usage-flexible than any other production small-block V-8 GM has built.

LS1 Block Machining Considerations

When it comes to LS1 block machining, there are a few key considerations to keep in mind:

• Bore Size: The LS1 block has a bore size of 3.898 inches, and it is important to note that the bore cannot be machined out much beyond this size. For larger bore sizes, inserts are available, but they are typically only suitable for short-cycle, drag racing applications. For more street-type use, it is recommended to use a 4.125-inch bore C5-R GM Racing Gen III aluminium block or the new LS7 block, which comes with siamesed bores and bore liners.
• Clearances: Aluminium blocks require greater clearances than cast-iron blocks because aluminium grows approximately twice as much as iron. This means that crankshaft main and rod, camshaft, piston-to-bore, and other clearances need to be almost double what they would be in an iron block.
• Oil Consumption: The increased clearances in aluminium blocks can affect oil consumption, as well as the required startup procedures and component life. It is important to use single-use, aluminium-compression gaskets to maximise sealing capability and minimise oil leaks.
• Valvetrain: The use of solid-lifter cams can be problematic in aluminium blocks due to the differences in thermal expansion between the aluminium block and the valvetrain components. The valve lash will start out very tight when the engine is cold, and as the deck height increases with temperature, it will reach its proper valve lash. Any hard use before the engine is fully warmed up could lead to broken valvetrain parts.
• Power Output: The stock LS1 aluminium block is generally suitable for naturally aspirated street engines below 650 hp. For centrifugally supercharged street engines of 700 to 1,200 hp, the cast-iron 6.0L truck block is recommended. Above 650 hp, steel main caps and a main-cap girdle should be used for added strength.
• Block Stiffness: The LS1 block features a deep-skirted bottom end, which improves stiffness and minimises noise emission. However, the deep-skirted design also affects oil scavenging in the separate bays, which can be addressed with a dry-sump oiling system.
• Cylinder Head Bolts: The LS1 block uses four cylinder-head bolts per bore, as opposed to the previous small-block's five per cylinder. It is important to use torque-to-yield (TTY) cylinder head bolts and ensure proper torque specifications are followed during assembly.
• Crankshaft: The LS1 uses a 3.622-inch crankshaft from the factory. When stroking the LS1, a common choice is to go with a 4-inch stroke, resulting in 383 cubic inches. This requires minimal clearancing of the block and does not require changes to the connecting rod length.
• Connecting Rods: The stock LS1 powdered metal steel connecting rods are press-fit to the piston pins and are not compatible with most aftermarket cranks due to differences in journal shape. Aftermarket connecting rods, such as those from Lunati, are designed to match their corresponding crankshafts and pistons, ensuring proper fitment.
• Pistons: When stroking the LS1, aftermarket pistons with a bore size of 3.903 inches are commonly used, resulting in a displacement of 383 cubic inches. It is important to check the piston-to-cylinder-wall clearance and ensure proper piston ring end gap during assembly.
• Balancing: When assembling a stroker LS1, it is crucial to balance the rotating assembly, including the crankshaft, connecting rods, and pistons. This can be a complex and expensive process, but it is essential for ensuring the long-term reliability of the engine.

LS1 Stroker Kits

For those looking to build a stroker LS1, there are aftermarket companies that offer stroker kits, which include a matched and balanced rotating assembly. Lunati, for example, offers LS1 Pro Series Stroker kits with displacements ranging from 347 to 447 cubic inches. These kits include a crankshaft, connecting rods, pistons, bearings, and piston rings, making them a convenient and cost-effective option for LS1 stroker builds.

LS1 engine block checks and cleaning

Overview

The LS1 is the original Gen. 3 small-block engine from General Motors, used in cars from 1997 to 2004. The LS1 is an all-aluminium, 5.7L pushrod engine with a bore and stroke of 3.898 inches and 3.622 inches, respectively.

Block Checks and Cleaning

Before beginning any work on the LS1 engine, it is important to perform thorough checks and cleaning of the engine block. Here are the steps to follow:

• Machine Shop Work: Start by taking your LS1 block to a machine shop for professional honing of the cylinders and installation of new cam bearings. This will ensure the cylinders are at the correct size and the cam bearings are in good condition.
• Initial Block Cleaning: Once you get the block back from the machine shop, perform a thorough inspection and cleaning. Use mineral spirits and 100% virgin acrylic lacquer thinner to clean the block and all metal components. Pay special attention to the cylinder walls and ensure they are free of any residue.
• Checking Bearing Clearances: Bearing clearances are critical for proper lubrication. Use Plastigage to measure the clearances between the crankshaft journal and the bearings. This will help you determine if the bearings need to be replaced.
• Checking Block-to-Rotating Assembly Clearances: With the crankshaft in place, temporarily assemble the rotating assembly to check for any interference between the assembly and the engine block. Ensure there is sufficient clearance for the connecting rods and pistons.
• Piston Ring Fitting: Piston rings need to be custom-fitted to each cylinder. Measure the gap between the ends of each ring and file them accordingly. Follow the piston manufacturer's recommendations for ring end gap.
• Final Block Cleaning: Before beginning the engine assembly, give the block a final cleaning. Use a soft bristle brush and a mild detergent to scrub the block, then rinse and dry it thoroughly. Ensure all threads and oil passages are free of debris.

Performing these checks and cleaning procedures on your LS1 engine block will help ensure a smooth and successful engine build or rebuild. Remember to always refer to a GM service manual for detailed instructions and torque specifications during the assembly process.

Frequently asked questions