The increased stresses generated by high-horsepower, high-boost big-block Chevy engines is stimulating new designs in billet cylinder heads at CFE Racing.
In the past, CFE introduced numerous billet heads for mountain motor applications in the 5.000-to-5.300 bore-space categories, but now the company is offering advanced spreadport designs in a solid chunk of aluminum for traditional 4.840-inch bore-space GM-style blocks. This new head closely resembles CFE’s popular 11-degree cast-aluminum spreadport BBC head but is built for more demanding situations.
“Power levels have increased and there’s growing levels of interest in turbo and supercharged applications,” says CFE’s Scott Kieffer. “This head raises the bar in terms of durability.”
In addition to performance potential the head offers, the billet construction removes any concerns that a porous casting may present, even solid castings that take the water jackets out of the equation.
“Continuous hard running and high cylinder pressures can lead to impregnating the metal with carbon when running gasoline,” warns Kieffer. “Also, the heat and pressure will add more fatigue to a casting than with a billet head.”
Billet also has advantages for cylinder head specialists when repairs are warranted, especially if broken parts lead to shrapnel scarring up or penetrating the head.
Benefits of billet
“Billet is much more receptive to welding and machining, if needed,” adds Kieffer.
Those racers looking to upgrade from CFE’s 11-degree spreadport BBC cast heads will be relieved to know that most components such as rocker arms, shafts, head-stud kits, headers and valve covers will carry over.
This head can help add power as well as improve durability.–Scott Kieffer, CFE Racing
“It shares a lot of the dimensions, so parts interchangeability is there,” says Kieffer. “For someone interested in switching over from the existing cast head, there’s more latitude to do so because parts will be reusable. And cylinder blocks are not an issue. Any 4.84-inch bore space block that already accommodates a Big Chief-style head will work.”
The CFE billet 11-degree spreadport head is patterned after the cast version but with a few options and restrictions. Presently it is not available with water jackets. But it will be offered in either oval or rectangular port configuration. In fact, CFE offers numerous intake port and combustion chamber designs to suit specific racing applications.
“It really depends on the size of the engine,” says Kieffer, noting this head works best with engine displacements under 700ci. “And also what intake manifold will be used.”
In most situations, the intake manifold will be fabricated to mate up with the heads. Every billet head is built from scratch, so the intake ports are going to be unique to the top end of the motor. CFE does work with a cast aftermarket blower manifold for traditional GMC-style Root superchargers. It can be machined to match the ports and certain deck heights. However, for carburetors and fuel injection, as well as some supercharged engines, custom fabricated manifolds will be required — either from CFE or another capable fabricator. Custom intakes provide the builder with flexibility in injector and fuel-rail locations as well as plenum design and throttle-body sizing.
Port size and shape options
“Even when you fab a blower intake, you have a recognize the forces from the supercharger on the intake,” says Kieffer, noting there are issues with the weight, engine speed and belt pressure. “It literally wants to crush the front two runners and tear the back two in half.”
To facilitate quick pit work and reduce maintenance costs, CFE machines O-rings on the intake side. That provides excellent sealing and negates the need to have custom gaskets cut to match the ports.
Racing setup — such as vehicle weight, tires and gearing — will be considered along with engine speed, boost and type of fuel when consulting with CFE on port and combustion chamber design. The head will support intake valve sizes up to 2.520-inch and exhaust up to 1.860-inch. Bronze alloy valve seats are standard and usually recommended. CFE also installs 11/32 steel guides, although smaller 5/16 guides are available for those builder concerned with valve weight, and alloy guides are available but not recommended for exhaust.
“The valves needed for these heads have relatively long stems,” explains Kieffer. “It’s helpful to support the stem and give the guide more durability.”
Works best with big cubes
With the head’s 11-degree valve angles, there is more freedom in shaping and sizing the combustion chamber.
“Eleven degree is quite versatile. It serves well for boost and injected alcohol applications,” boasts Kieffer. “We have latitude in the middle 60cc range up to mid ‘80s for the combustion chamber. This also gives the builder added flexibility in piston design and controlling the compression ratio.”
CFE can also machine a receiver groove around the chamber for O-ringed blocks.
The billet 11-degree spreadport head is better suited to work with bore sizes from 4.500- to 4.600-inch, or perhaps a little more if the block allows. That range matches up well to the pistons and rings readily available in the aftermarket.
“If someone wanted a 4.350-inch bore for a small cubic-inch motor, we could look into that,” says Kieffer.
The head is also designed for a 3/4-inch reach spark plug, and step washers are available and certainly recommended for blown applications.
“Those engines can be more maintenance intensive with disassembly and assembly,” says Kieffer. “With the step washers you don’t have to worry about misplacing a washer in a rapid pit thrash.”
CFE says the new billet 11-degree spreadport head is a perfect alternative for big-cube, high-boost racing where the builder wants an alternative to popular Hemi-style engines.
“Like truck pullers who are die-hard Chevrolet guys,” sums up Kieffer. “They don’t like Hemis and want to run a Chevy. This head can help add power as well as improve durability.”