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  1. #1
    Blown, Stroked, & Sprayed

    Ed Blown Vert's Avatar
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    Exclamation Chevy Nascar Engine - Nascar's New Chevy

    Chevy Nascar Engine - Nascar's New Chevy
    It says a lot about the current nature of the sport that the most successful new engine in American racing today is a 90-degree pushrod V-8. But if you look past the pushrods, the cast-iron block, and the ancient Holley four-barrel carburetor, you can see that otherwise, Chevy's R07 is as advanced as any racing engine in the world. Guys who build winning engines for F1, Indy, and Le Mans will look inside Chevy's latest NASCAR powerplant and see the very same hardware and technology they use. The external packaging looks a little anachronistic, that's all.
    As soon as GM Racing introduced its previous NASCAR engine, the SB2 (small-block, generation 2) in 1998, the company went straight to work designing its replacement. The R99 (racing engine, '99) and R03 engines were successfully developed and submitted to NASCAR for competition, but never approved by the sanctioning body. While GM Racing was working on its R05 engine, talks were under way between NASCAR and the manufacturers regarding a proposed "engine of the future" to parallel the chassis program that produced the NASCAR Car of Tomorrow. While those discussions never completely came to fruition, they did generate an "engine parameters list": a set of min/max dimensions and specifications that define the box in which NASCAR's manufacturers are allowed to compete.
    These specs, numbering around 50 items, cover everything from basic layout and materials (pushrod V-8, cast-iron block) to individual component dimensions and weights. For example, pistons can weigh no less than 400 grams, connecting rods no less than 525 grams. The camshaft can be no higher in the block than 6.150 inches above the crankshaft centerline; minimum deck height is 9.00 inches. Valve angles and locations must also fall within an allowable range, and maximum compression ratio is 12:1. The displacement limit is the traditional 358 cubic inches, while the maximum allowable bore diameter is 4.185 inches.
    The R07 was designed to reach out to the edges of this carefully defined box. The previous SB2, closely based on the original small-block Chevy introduced in 1955, was far from optimum under the regulations, especially when compared with the newer, purpose-built NASCAR engines built by Dodge and Toyota. The R07 is the first clean-sheet engine design by GM Racing for NASCAR competition.
    As an all-new engine, the R07 shares nothing with the old small-block Chevy or with GM's current production V-8s. Let's start with the block. Its bore spacing is 4.500 inches, compared with 4.400 inches for the small-block and Gen III/Gen IV engines. That means the crank, cam, and other major components will not interchange. However, the greater bore spacing allows coolant jacketing between cylinders, while previous small-blocks required siamesed bores to obtain cylinder diameters much beyond 4.060 inches. Also, the R07's block is cast in compacted graphite iron (CGI). Viewed under high magnification, CGI has a structure resembling sea coral-which makes it much stronger than traditional iron casting alloys. Blocks sinter-cast in CGI can be up to 75 percent stronger and significantly lighter at the same time.
    The cam is raised in the block to the legal maximum, which permits shorter, stiffer pushrods, while the 60mm cam journals allow a greater base circle for the NASCAR-mandated flat-tappet camshaft. The raised cam also makes room for two rows of integral oil galleys on either side, which supply the piston squirters. (Two more galleys are positioned on the outboard sides of the block.) The oil squirters keep wristpin and piston-crown temperatures under control. The squirters and plumbing were installed by the team engine shops on the SB2 engine, which required considerable machining and fabrication. So did the elaborate lifter-valley shields installed to prevent return oil from showering the camshaft, increasing windage losses. However, the R07 block features a cast-in-place cam tunnel. A minimum of 50 hours of hand labor was required to prepare the old SB2 block for competition. With all these features designed into the R07 block from the start, the teams are treated to a significant savings in time and cost.
    The new block also includes several safety advances. By incorporating the coolant and oil passages into the block casting, there are fewer external lines and fittings, reducing the possibility of fluid spills and fires in a crash. Also, the NASCAR-required mechanical fuel pump can be driven either from the left side of the engine or remotely via a cable from the rear of the camshaft to a rotary pump mounted near the fuel cell. The old small-block V-8's fuel pump is on the right, and thus more vulnerable to wall impacts.
    The R07's cylinder heads are a brand new day as well. The small-block's "mirrored" or "book-fold" head layout was compact and efficient back in 1955, but it had several drawbacks for performance use. For one, the valve layout places two exhaust valves adjacent to each other on the center cylinders of each bank, creating two large hot spots that are difficult to cool. On the R07, the valves are deployed in intake/exhaust order across the cylinder head, eliminating these hot spots. Additionally, each cylinder is fed coolant individually via the manifold passage cast into the central valley cover. (On the original small-block the outside cylinders were cooled first.)
    We would love to be able to show you the intake and exhaust ports of the R07, but those details are rather sensitive, and they vary among teams as well. GM Racing furnishes the head castings in raw, semi-finished form with the intake and exhaust passages left in their as-cast state, so teams can perform their own porting. In this and other aspects the R07 is unique, as the engine is not so much a product of GM Racing but a close technical collaboration between the factory and what GM calls its "key partner teams." GM Racing provides the foundation and framework of the engine, while the Chevy teams develop the engine into a winning package. When the R07 program was launched, these teams included Hendrick Motorsports, Richard Childress Racing, Dale Earnhardt Inc., and Joe Gibbs Racing. (Since then, RCR and DEI have merged their engine shops while Gibbs has moved on to Toyota.) The key partner teams meet with GM Racing's engineers once a month, and it was their input that produced many of the improvements found in the R07, including the design changes in the cylinder block and heads.
    In the last decade or so there's been a revolution in how NASCAR teams operate their engine shops. Now each one is a competent engine development company in its own right, with the ability to handle nearly any part of engine R&D. If NASCAR let them, many would be capable of building their own engines from scratch. As the sport has exploded, technical resources and personnel have flooded into NASCAR from every corner of the globe. For example, the manager of the engine department at Childress is Nick Hayes, formerly the technical director at Cosworth Engines. So these engine shops (which are really more like factories; Hendrick alone builds more than 300 engines per year) are more than capable of handling their own cylinder-head and manifold development using CFD (computational fluid dynamics) and other advanced tools.
    And while the NASCAR teams once relied upon outside companies like Crane or Competition Cams to perform their camshaft and valvetrain development, that work is now brought in-house as well. So we can't really talk about valve lift, duration, or other valvetrain specs either. That is proprietary information, as they say, and also varies with application. Different venues-speedways, short tracks, and restrictor-plate events-call for different combinations. Precise valve locations and included angles are also closely held secrets. However, here is one interesting and revealing data point: According to our sources, all the builders are currently using rocker-arm ratios of 2:1 or greater.
    With a maximum cylinder bore of 4.185 inches, the 358ci displacement limit is achieved with a stroke of 3.25 inches. (However, builders may juggle those dimensions a bit so they can perform multiple rebuilds without exceeding the bore limit.) Connecting-rod lengths are typically in the 6.00- to 6.200-inch range, constrained by the 9.00-inch deck height rule. NASCAR limits engine speed by specifying the allowable transmission and final drive ratios for each track. The approach is not as hard and fast as, say, an electronic rev limiter, but it does keep engine speeds in the 9,300- to 9,600-rpm range.
    That's pretty fast for a pushrod V-8, especially given the 800-mile service life that must be designed into the R07 to make it through practice, qualifying, and race day at a typical NASCAR Sprint Cup event. And it's pretty darned impressive when you think about it. Consider this: when you run the numbers, at 9,500 rpm, mean piston speed is 5,145 feet per minute with a maximum velocity of 8,380 ft/min at a crank angle of 76 degrees. Maximum positive piston acceleration is approximately 3,100 g, while the negative acceleration is nearly minus 5,300 g. How on earth can a big old 358ci pushrod V-8 live under such tremendous and sustained abuse, handling forces heretofore seen mainly in F1 engines? There's one part of the program that is no secret at all: extremely good parts and very careful assembly.

    Photo Gallery: Chevy Nascar Engine - Nascar's New Chevy - Hot Rod Magazine



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  2. #2
    20K+ posts in 2004
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    I was at DEI last April and I saw RO7 heads and engines being assembled. Neat stuff

  3. #3
    Catfish for Breakfast Bobby97SS's Avatar
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    A little behind the times on this one bro. Probably why a Dodge won Daytona, the chevy guys couldnt find the distributor.

  4. #4
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    2000 Pontiac Trans am M6

    i get to build those at my school :P

  5. #5
    11 years of bangin gears cammed goat's Avatar
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    Looks like a pretty stout motor. Hopefully we won't hear anymore horror stories about engine failure i.e. broken valve springs, destroyed pistons etc.

  6. #6
    Member cuervo25_1's Avatar
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    Siameased Bores? that don't sound good at all for a race engine. When I had the Monte even though I had a 400 sb I was carefull because of that reason.

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