The LS6 Lower End
The LS6 and the LS1 use an all-aluminum block. It's a "deep-skirted" design (block structure extends below the crankshaft centerline) with six-bolt main bearing caps (four vertical bolts and two horizontal bolts per cap) and head bolt threads deep in the main bearing bulkheads (for minimal block distortion and maximum head gasket clamping force). LS1/6 blocks are semi-permanent mold castings of 319-T5 aluminum. The LS6 case is different from LS1 blocks in the design and strength of the main bearing bulkheads.
LS6's valley-mounted oil separator...
LS6's valley-mounted oil separator is similar in concept to the system used a decade before in the LT5. It uses internal baffling to force the crankcase vapors in a circuitous flow. In the process, the oil separates and drains back into the engine.
As the pistons move up and down, they force air in and out of the spaces (or "bays") beneath them. At high rpm, this reciprocating air flow is violent and really whips up the oil. While the LS1 block has some machined openings between bays, the LS6 block, because the engine has about 500 more usable rpm, needed larger windows at the base of each cylinder to better accommodate "bay-to-bay breathing."
Obviously, cutting windows at the bottom of each cylinder reduces the strength of the block's key structural area, the main bearing bulkheads. With 40 more horsepower, 400-500 more rpm and even more powerful derivations of this engine to come, the block needed to be even stronger than it would be without the windows. In their ruthless pursuit of power, Juriga and his engineers had to do more than simply reprogram their CNCs to cut those windows. Finite element design work along with a lot of thrashing engines to death on the dyno eventually resulted in the special LS6 block with bay-to-bay breathing windows and more strength than the LS1 block.
Like the LS1, LS6 uses centrifugally-cast, gray-iron liners cast into it at the foundry. Their bore is 99 millimeters (3.8976 inches). In 1997 and 1998, the LS1 could not be overbored. But, for 1999, liners changed and a service overbore of .010-inch was possible; this carries over to the LS6.
Looking at these side views...
Looking at these side views of the LS6 intake port (left) and the LS1 intake port, it's very easy to see the difference in the port floors and the short-turn radii.Photo: GMPT Communications
The LS6 crankshaft is the same cast, nodular iron unit with rolled-fillet journals used in the LS1 since 1997. Its stroke of 92mm (3.6620 inches), makes the LS6's displacement 5.665 liters or 345.69 cubic inches. Drilled main bearing journal centers reduce weight and assist in bay-to-bay breathing. For the 2001 model year (MY01), the reluctor wheel, pressed onto the crank to trigger the crankshaft position sensor, was redesigned to enhance sensor signal output. For MY01, all Gen IIIs use a new main bearing having reduced diameter variation. That allowed a slight decrease in main bearing clearance which reduces the potential for bearing knocks during starts in extremely cold weather from engines having bearings on the high-side of the variation. Lastly, LS6 cranks use a lightweight harmonic damper having an aluminum hub which cuts 2.6 pounds.
The 6.1-inch, sintered, forged and shotpeened PF1159M steel connecting rod introduced in 1997 carries over to the LS6. Beginning in MY01, all Gen III rod cap screws are stronger through a change in manufacturing process used to heat-treat and roll the screw's threads.
LS6 puts out more power and runs faster so it has a brake-mean-effective-pressure (bmep) that peaks about 15 percent higher than LS1's. Because of this, LS6 needs a more robust piston. The LS6 unit is cast of a eutectic aluminum/silicon alloy called "Mahle 142." Both M142 and the previous material, M124, also contain small amounts of copper and nickel, but M142 has slightly more of both. Mahle 142, offers increased strength and less expansion at high temperature. That offers better control of piston-to-bore clearance, both at the skirt and the ring lands which prevents piston noise along with enhancing durability and oil control. Because the LS6 piston material has more favorable expansion characteristics, the slight barrel-shaped profile used in the machining of the piston had to be changed, too.
Camshaft And Valvetrain
While the camshaft in the LS6 is more aggressive than the LS1 cams, its basic construction is the same: machined from a steel billet, rifle-drilled for less mass and with a camshaft position reluctor just ahead of the rear journal.