Back in August when General Motors introduced the all-new GT2 class Corvette C6.R, it ran downsized 6.0-liter version of the 7.0-liter V8 from the long-dominant GT1 car. At the launch, Corvette Racing program manager Doug Fehan told us the 6.0-liter was just an interim engine. With revised GT rules on tap for 2010, GM was already planning a brand-new engine for its race Vette.

Unlike the 6.0/7.0, which is a ground-up race engine that only shares basic architectural dimensions with the production small block, the 2010 C6.R's V8 is a new 5.5-liter unit that will indeed be derived from the production engine found in roadgoing Corvettes. In fact, the 5.5-liter race engine will be built at GM's Performance Build Center alongside ZR1 and Z06 V8s.

Fehan has confirmed that the 5.5 is running on the dyno and will make its race debut at the 12 Hours of Sebring in March. We don't have any additional details on the new engine yet, although we were told earlier that it is based on the next-generation production small-block, which we expect to see in the Corvette soon.

It is not the displacement that is the news here but the new block being derived from a production block. The GenV block is the news, and the significant improvement is the raised camshaft. Raising the camshaft shortens and stiffens the pushrods and reduces the weight of the valvetrain. All of which will have a very positive impact on a race motor, much the same way the R07 nascar motor improved on the prior NASCAR motor. For a street motor this improvement is marginal in impact due to the practial rpm limits, the LS7 redlines at 7100 while the R07 turns up to 9500 rpm. The second benefit of a raised camshaft motor is the increased angle that the pushrods enters the head relative to the V angle. This allows the the pushrods to be placed out of the intake port path easily, making for straighter, larger intake ports, again look at the R07 intake port design. Additionally it leaves more room to place the SIDI injector. The Wards article on a SIDI LS engine stated that the engine had revised porting compared to a current GenIV LS head. The raised cam block will be compatiable with the cam phaser technology. The reason it is not currently used on performance versions of the LS engine series is because it has about 50 degrees of adjustment and that large spread combined with a high lift /long duration cam would lead to the real possibility of valves contacting pistions or exceedingly deep valve relief cuts which tend to weaken pistons and create hot spots in the piston face. The GenV block will mean, better breating heads, SIDI, increased compression, greater power density per litre, greater fuel economy, and reduced emissions. In all likely hood cam phasers will see increased fitment over the LS engine line due to the emission benefits that they have. There are ways to limit the range of phasing down to 20/25 degrees so that they will work with a "performance" cam. Were GM to utilize concentric cam technology it could independently vary the timing on both the intake and exhaust lobes of the cam to maximise the benefits of VVT.

As an aside the raised cam block will make the utilization ot the previously designed and as to now unuesd three valve head design much easier. Simply twisting the valve layout 12/15 degrees lets gm use a single conventional rocker arm to control the exhaust valve. Eliminating the crossover pushrod and the second rockerarm, making the three valve head simpler and less expensive. Think of that advantages of a compact, multivalve, VVT, SIDI, AFM, pushrod V8 compared to the "modern" DOHC engines we see today in terms of cost and packaging.

http://www.gminsidenews.com/forums/1937897-post92.html

Think of that advantages of a compact, multivalve, VVT, SIDI, AFM, pushrod V8 compared to the "modern" DOHC engines we see today in terms of cost and packaging.