 See how the middle cylinder’s exhaust valve pockets are adjacent – mirror-imaged – in the SB2? That’s been abandoned in the R07. |
For example, CFD is commonly associated with racecar aerodynamic development of the body and chassis, but it also can be used to analyze the behavior of fluids like coolant flow through the Chevrolet R07's block and cylinder heads. FEA was used to analyze the strength and minimize the weight of the R07's block and cylinder heads. These are two main areas that the R07 has improved over the SB2.
"Although we use many of the same engineering tools, the timeframe for racing engines is much shorter than it is for production engines," Suhy notes. "The rapid turnaround in racing allows us to get feedback on the accuracy of GM's computer simulations and models very quickly. The same programs can then be refined to make them more accurate when used to develop future production engines." So, the production side does get a return from the racing side: improved modeling accuracy.
R07 Technical Features
The R07 continues the camshaft-in-the-block, pushrod/two-valve layout used since the introduction of the first-generation small-block V8 in 1955. No overhead camshafts in Cup racing!
Per NASCAR specifications, the Chevrolet R07 displaces a maximum of 358 cubic inches with a maximum cylinder bore diameter of 4.185 inches. The block is a precision iron casting with integral oil and coolant passages that eliminate the need for most exterior lines – as were used in the SB2 to optimally route these fluids about the block.
The distance between the Chevrolet R07's cylinder bores is 4.500-inch vs. 4.400 inches in the SB2 small-block. This wider bore spacing improves coolant circulation around the cylinder barrels (uniform cooling) and the R07 block design minimizes temperatures at critical locations. An ideal for a Cup engine builder is to get all eight cylinders operating at peak efficiency for the longest amount of time – eight identical power supplies. Managing the heat at each cylinder is critical for this goal.
NASCAR teams usually spend hours modifying SB2s to make a weight (trimming excess metal on them via CNC machines and by hand); adding oil squirters to cool the pistons; and installing outside plumbing on the block to route coolant to hot spots between pistons. Still, Chevy teams were scuffing pistons from excessive heat (making power) in some races. The R07 counters this time-consuming work and issue.
The R07 block has a new six-bolt head bolt pattern (yes!) instead of the small-block's traditional five-bolt design. The revised head bolt pattern improves head gasket sealing and reduces cylinder bore distortion. This is a huge change from the stock production-based race engines before, and helps keep the individual cylinder efficiency optimum.
 Raw head casting further showing the exhaust port spacing of the R07. |
Another monumental change is that the R07's camshaft is located higher in the block than the camshaft in the SB2 – the distance between the centerlines of the crankshaft and camshaft is greater. Other Cup engines have had this design advantage for years (although the Dodge engine pays a weight penalty these days).
The raised cam operates pushrods that are now shorter and stiffer. This improves valvetrain dynamics and stability as rpm increases; consequently, the more air you can deliver to the cylinder at this higher rpm = more fuel = more power.