427? I say LS7...

  Now, I'm not pointing my finger at names like '911 Carrera' or 'Corvette'. While a lot of nostalgia is associated with those names, they have been carried through a long lineage based on a particular formula. They are established within the automotive communities and each carries considerable weight.

2010 Chevrolet Corvette Z-06

   On the other hand, there are names such as 'Impala' and 'Malibu'. When we hear these names we are taken back to visions of classic muscle cars, not front-wheel drive half-measures with styling and performance as bland as a floor tile. It isn't necessarily deception. It simply evokes memories of something that it itself isn't.

   So it was with amusement that I started hearing the Corvette's LS7 referred to as a 427. When I think 427, I think of old big-block Corvettes. It isn't nearly as much of a stretch as the example mentioned in the previous paragraph, but it does have that aroma. It is indeed actually a 428. And a small-block 428 at that.

Production LS7 in a C6 Corvette Z-06

   Perhaps I'm splitting hairs when I say that the LS7 is actually a '428', but the fact is that its actual displacement is indeed 427.7 cubic inches (The 427 big-block of yesteryear was 426.7 cubic inches making it an actual 427). The LS7 is also an aluminum LS based small block. It's actually the largest displacement production small block General Motors has made.

LS7 Cutaway Drawing

   Based on GenIV LS block architecture, the LS7's cylinders are siamesed, meaning there are no cooling passages between the neighbouring cylinders in each bank. Eliminating these passages means engineers could increase both bore size and block strength. Other changes to the standard block included sleeved cylinder bores and a larger 4.125inch bore and longer 4.00inch stroke.

   The standard 4.4 inch bore spacing is retained, however required  the pressed-in cylinder liners. The crankshaft and main bearing caps are forged steel for durability, the connecting rods are forged titanium, and the pistons are hypereutectic. Titanium intake valves are made by Del West and have grown to 2.20 inches. The sodium-filled exhaust valves are up to 1.61 inches.

2010 Chevrolet Corvette Z-06 side view

  
   All of this results in five-hundred and five normally aspirated horsepower at 6300rpm, and 470lb-ft of torque at 4800rpm.


   It is interesting to note that during GM's reliability testing of the LS7 in its prototype phase, it was remarked to have been repeatedly tested as 8000rpm capable. Its power wasn't recorded at those higher speeds however, due to the constraints of the camshaft's hydraulic lifters and the ability of the intake manifold to flow the air required at those higher engine speeds.

Corvette C5-R GTS

  The LS7 didn't officially debut until the third quarter of 2005, coming in the 2006 model year C6 Corvette Z-06. It is believed to have spent time prior to its 2005 debut under the hood of the Pratt & Miller developed Corvette C5-R race car. This was General Motors first factory supported racing effort since the Corvette GTP's of the IMSA GT Championship in 1989. The C5-R started with the LS1 derived 366 cubic inch (6.0L) motor, but it was quickly replaced with what was only known as a '7.0L 427' during its first racing season (1999). The C5-R ended up using this powerplant for the remainder of its racing career.

Corvette C6.R with LS7.R

   While the '7.0L 427' that was used to power the C5-R was never actually called out as an LS7, it isn't at all a stretch to assume that General Motors was using the C5-R racing effort as a development bed for what would eventually be released as the production LS7. The C5-R ended up going on to many wins at the 24 Hours of Daytona, the 12 Hours of Sebring and the 24 Hours of Le Mans, as well as championships in the American Le Mans Series.

The LS7.R

   Alongside the 2005 debut of the LS7 powered Corvette Z-06, was the debut of the LS7.R powered Corvette C6.R GT1. Like the C5-R, the C6.R was built by Pratt & Miller, with factory support from General Motors. The LS7.R powerplant produced 600hp and is based closely on the production LS7. It is built by Katech Engine Development. The C6.R GT1 recorded first and second place finishes in the 24 Hours of Le Mans in its debut year (2005). It also went on to dominate the American Le Mans Series championship, the European Le Mans Series, and the FIA GT Championship.

The Number 3 & 4 Corvette C6.R GT1 Cars

   In 2009, The C6.R GT1 race cars that were powered by the LS7 derived LS7.R ran their last competition outing at that year's 24 Hours of Le Mans. The GT1 cars were retired so that more time and resources could be used in developing the C6.R GT2 cars that were running 5.5L and 6.0L powerplants (the 5.5l units were reportedly in development for the C7 Corvette).

   No Corvette is as steeped in rich racing heritage than the LS7 powered C6 Z-06. Its 7.0L '427' has in one form or another powered Corvette's competition efforts for ten successful years. From the C5-R (1999-2004) to the C6.R (2005-2009), its 7.0L push-rod motors have beat some of the best the world has to offer. 

   So the next time you see a sixth-generation Z-06, give a nod in homage to its close siblings that had the performance and reliability to endure and win some of the most grueling and legendary races in automotive history.        

          
-SSM
     

For more information on the 2010 Corvette Z-06 pictured in this story, or to book a Test Drive, click here.