To create a 418, the bore...
To create a 418, the bore needs to be opened up to 4.080 and the stroke elongated to 4.000. GM LS3 main caps are torqued to spec in order to maintain load conditions on the block before machining. The block is then set up on a Rottler F-67A three-axis CNC machine and the deck height is measured against the stated height of 9.240 inches. After three passes, the deck height is set to 9.238 inches.
Part 1
When introduced in 1997, the diminutive 346ci LS1 was the proverbial tip of the displacement iceberg. GM has since taken the LS1 architecture and developed a whole host of block and head designs for both assembly-line and aftermarket uses. For enthusiasts looking for max performance, the cast-iron LSX block can achieve more than 500 cubes in its tall-deck configuration.
Things really got interesting in 2006, when GM launched the 427ci LS7. Standard equipment on the 505hp Corvette Z06, the LS7 featured new high-flow, rectangular-port cylinder heads. A year later, the company adapted the rectangular-port design into a mainstream engine offering called the L92. Compared with previous "cathedral port" heads such as the LS2 (which flowed 260 cfm on the intake side and 180 cfm on the exhaust at 0.600 lift), the L92 head had tremendous flow (316/189 cfm) and excellent velocity. In fact, a version of the L92 head is currently used on the base Corvette's LS3 engine.
Not long after the L92 was introduced, enthusiasts started bolting the engine's heads and intake onto 6.0-liter (and larger) blocks and making LS7-killing power numbers. According to Jason Mangum of Texas Speed and Performance (TSP), "Whereas the most-popular stroker combinations were LS2-based 402s and 6.0-liter iron 408s, the market has shifted to the L92/LS3 aluminum 6.2-liter block and LS3 heads. This an excellent block for the street, as the casting incorporates numerous revisions to increase strength.
"In stock form, the engine has a 4.065 bore and a stroke of 3.622, which yields 376 cubic inches," he continues. "Due to the thickness of the cast-iron cylinder liners, the LS3 block can be bored and stroked to 418- or 427-inch configurations. With a set of our ported LS3 heads and an aggressive cam, we can achieve 650 hp with the 418 and more than 675 hp with the 427."
TSP offers LS3 engine packages in both of the aforementioned displacements, in short-block ($4,095) and long-block ($7,399) forms. Mangum and company will even sell you a turn-key engine complete with an intake, fuel-system components, and headers for a quite reasonable $9,607.74.
Over the next few pages, we'll follow a 418ci LS3 as it takes form at Sunset Racecraft in Lubbock, Texas. (Note: Sunset typically handles the machining and short-block work for TSP, then ships the combo to TSP headquarters in Wolfforth for final assembly. In the case of our test engine, however, the entire job was performed at Sunset, with help from TSP lead tech Joseph Potak.) In next month's issue, the finished product will be bolted to a dyno, and a number of camshaft and cylinder-head changes will be performed to reveal the true power potential of the engine. If you're looking for a durable and affordable alternative to an LS7, we think you'll find that this low-buck LS3 stroker could be just the thing.
 Once the block is set up for...  Once the block is set up for boring, the bore size and center are determined. The boring head is attached, and the CNC machine is programmed with the bore center, deck height, boring stroke, and the amount of material needed to achieve the desired measurement. Since the bore specified was 4.075 inches, a single pass was all that was necessary to bring the bores to the final spec. The process is repeated on each bore, and measurements are taken to ensure that the desired bores are obtained. |  In order for the longer connecting...  In order for the longer connecting rods (6.125 inches vs. a stock length of 6.098 inches) to clear the bottom of the bore with the planned crank/rod combination, a carbide bit is used to remove 0.006 of aluminum at the bottom edge, straight across each bore. Once the aluminum is removed, a sanding roll is employed to smooth and radius each cut to ensure that a piston will not nick the area on the downstroke. |  The block is then moved to...  The block is then moved to a Sunnen CV616 Cylinder King honing machine and set up in a fixture. A cone-shaped sanding disc is put over the top of each cylinder and operated until the top edges of the cylinders have a slight bevel. The final bore size is a combination of piston bore (4.075 inches) and ring gap (0.0050 inches). A BJH Products torque plate is utilized with a Cometic MLS gasket, and the 10 15mm head bolts are torqued in sequence to 60 ft-lb. A total of three passes with different-sized stones are made to achieve the desired bore of 4.080. A soft hone is then performed on each cylinder for three to four strokes to remove any minor scratches. |
 After pressure washing the...  After pressure washing the block, a set of Durabond CH-23 cam bearings are lined up in installation order. After ensuring that the oil holes in the front bearing line up with the oil-gallery holes in the block, a bearing-installation tool and a dead-blow hammer are used to drive the bearing into position. The process is repeated until all the bearings have been installed. Both the bearings and a "test" cam are then lubricated with 30-weight oil and slipped into position to ensure that the cam rotates freely. |  The target main-bearing clearance...  The target main-bearing clearance for the engine is 0.0020-0.0025 in. After removing the 20 main bolts (side bolts weren't in for the procedure), a set of ACL main bearings are installed dry in the front, and the ARP 2000 main bolts are lubricated with oil. The main caps are torqued first on the inner bolts (15 ft-lb plus 80 degrees rotation) and then outer bolts (15 ft-lb plus 53 degrees). A main-bearing dial gauge is used to measure clearance, and the readings are transferred to the blueprint sheet. |  The rotating assembly is balanced...  The rotating assembly is balanced on a Sunnen DCF-2000 electronic balancer. After determining the total bob weight of the number 1 and 2 rotating and reciprocating components, the figures are entered into the machine, and the Eagle ESP forged crank is prepared for balancing. Bob weights are affixed so the computerized balancer can determine where weight has to be added or subtracted on each counterweight. |