Rumors have swirled about it for a couple of years, but it now appears the introduction of a new 380-horsepower LS6 engine is a fact. Better still, its intro is right around the corner-as an option in the 2001 Corvette Hardtop.
Chevrolet has been pretty quiet about the new LS6, but from documents we've seen, the new engine will be available in '01 'Vette Hardtops under RPO Z06. The Z06 option is a race-ready package that should give the Corvette better than 1g cornering capability (thanks, in part, to a second-generation active handling system), along with the added thrust of the all-new LS6 engine.
Of course, the original LS6 engine of 1970 was a big-block. This time around, the LS6 is a modified version of the LS1 small-block. Enthusiasts will spot it immediately, thanks to a bright red "beauty" cover, compared to the LS1's black engine cover.
But the LS6 isn't simply a warmed-up LS1. There are significant mechanical upgrades that complement the engine's 35 extra horses. We'll detail those improvements in a moment, but first we'll delve into where those extra horses came from.
Heavy Breathing
Since an internal combustion engine is really just an air pump, getting more air in and out of it will result in greater horsepower. That's just what the engineers did with the LS6. A larger-diameter mass airflow sensor (from a Vortec truck engine) and a revised intake manifold help draw more air into the engine (higher-flow injectors bring more fuel, too). Revisions to the composite intake manifold include larger intake passages and runners that have been redesigned to eliminate some of the LS1 intake's "dead spots," thereby increasing the volume of air getting to the cylinder heads.
Speaking of cylinder heads, the aluminum versions for the LS6 feature smaller pent-roof combustion chambers. This bumps compression to 10.5:1, compared with the LS1's 10.1:1 figure. Also, the LS6 heads' intake and exhaust ports are cast more precisely, which enhances overall volumetric efficiency.
Putting the squeeze to the new heads are new cast M142 aluminum pistons. Compared to the LS1's slugs, these pistons have a slightly barrel-shaped profile. The M142 alloy is said to increase engine durability, particularly under heavy-duty, race conditions.
The biggest contributor to the LS6's 380 horsepower (and 380 ft-lbs of torque) is an all-new, higher-lift camshaft. We don't have all the details on the cam, but it allows the engine to rev to 6,600 rpm (up from the LS1's 6,200 redline). To keep up with the extended rev range, the LS6 gets stronger valve springs, too. Although based on the same steel wire as the LS1's springs, the new springs are wound tighter for a higher spring rate.
To send out air in the engine, the LS6 features all-new cast-iron exhaust manifolds. They're more durable, flow better, and are a lot less expensive that the dual-wall stainless manifolds of the LS1.
Finally, to manage the increased airflow and lumpier cam profile, the LS6 features a revised PCM computer.
Structurally Speaking
As we mentioned, the LS6 is more than just power upgrade of the LS1. Chevrolet developed the engine with racing in mind and significantly upgraded its structure and tolerances.
One of the improvements includes the elimination of machined holes in the aluminum block's bulkhead in favor of honed "overtravel" windows. This allows better cylinder bay-to-bay breathing. On the pistons' downstroke, they push air back toward the crankcase, creating backpressure that sacrifices some power. The overtravel windows help reduce this backpressure.