The new bigger big block – 5-inch bore heads and blocks, are nothing new to the arena. During the late 1980′s, Pro Stock teams were using the common large bore space big block engines of the time, namely the 4.900″ for the Ford camp and 4.840″ on the GM side. In response to the wishes of GM engine builders and in an effort to align the two combinations from a competition standpoint, the NHRA made provisions to allow the use of 4.900″ blocks, and when the first iteration of the GM Pro Stock engine, the Oldsmobile DRCE was released, it fit within that new regulation from the NHRA on bore spacing.

During this time Dart Heads and owner Richard Maskin were knee deep in Pro Stock championships with these very engines that have continued to grow to 5.300″+ bore spacing through 2011. Building 5-inch bore space engines use to require a fat wallet, and while it still isn’t exactly cheap, Dart is helping the racer build these huge engines at a better price point. For example is Dart’s cast 14 degree Big Chief 5-inch bore space head on their 708ci, 1462 hp naturally aspirated motor showing in their booth.  Dart had developed this engine over the last year and has helped simplified things for the racer, by adjusting the rocker geometry to use typical off the shelf, non-Z rockers.  Dart even sells the rocker mounting pad with the heads to simplify valvetrain geometry.

The 14 Degree Big Chief head brings many of the most powerful innovations from highly competitive Pro Stock racing to a production cylinder head. The competition style spread oval ports, raised runners and highly efficient combustion chambers provide a serious racing head that blends efficiency and reliability with awesome power. The 5-inch bore space design is perfect for high power alcohol and nitrous builds that will exceed 7,000 rpm. Of course if you want to go crazy with their billet heads, they have that available as well.

Dart’s billet blocks is where a racer can go crazy designing virtually any engine combination imaginable. With completely custom machining options for each block, Dart big block Chevy billet blocks allow for virtually unlimited choices in bore centerline, deck height, bore diameter, and lifter and cam options. Every billet block is machined from a solid block of ultra-lightweight, forged 6061 aerospace aluminum alloy, then heat treated with a proprietary process that results in ultimate strength and stability for extremely stressed racing engines.

From spread bore spacing, to modified head bolt patterns, to special lifter locations, altered cam shaft locations or high capacity water jackets Dart billet blocks turn your concepts into a reality.

Big Chief 5-inch Bore Space Cylinder Heads

• Premium alloy: Dart aluminum heads are cast from virgin 355-T61 aerospace alloy for superior strength and integrity
• 5-inch cylinder bore spacing
• 14 degree rolled valve angle and raised ports for excellent air/fuel flow characteristics
• 5-axis CNC machined intake and exhaust ports and combustion chambers
• Huge 2.575″ intake and 1.900″ exhaust valves
• Stainless steel or titanium valves available, oval port version comes standard with copper beryllium seats and titanium valves
• Spread port design eliminates inefficient port locations, increasing power and consistency
• Raised spark plug location improves flame travel for a quicker, more complete burn, producing more power
• Rocker stands and roller rockers available for 5.000″ Big Chief, call for more info