Although converting to an 18-degree top end requires some specialized valvetrain components, it's not as exotic as some people think. "For a max-effort small-block, the 18-degree heads really are hard to beat," says Noe. "Even though a lot of unique parts are required, if the engine is planned and built specifically for 18-degree heads, the cost is not unreasonable. Compared to a conventional 23-degree motor, all you need to complete the swap are 18-degree-specific pistons, intake manifold, headers, offset lifters, and shaft-mount rockers. Since those are parts you'd probably buy when building any all-out small-block, the cost difference between a max-effort 23-degree motor and an 18-degree motor isn't as much as it may initially seem."
Researching and developing a cylinder head is an exhaustive process. Trick Flow starts with a list of objectives it wants to accomplish in terms of performance, price, and parts compatibility. Sometimes a benchmark is established based on a competitor's head, and the goal is to improve upon its performance. "The actual design process starts when we develop a flowbench model and test several ports and chamber designs. Once we have a starting point, we then make foundry tooling to cast the heads, machine them, and then implement the first port and chamber design," Noe explains.
With a working model now in hand, the head is flowed and dyno-tested, and then after several revisions the final port and chamber design is determined. This final design is dyno-tested for both power and durability. "After 40 straight hours on the dyno in which the loads and rpm are continuously cycled, we then disassemble the heads and check all the clearances and measurements to make sure they are within acceptable limits. We also check all the wall thicknesses of the castings to ensure that we have adequate wall material everywhere. It's not until we are satisfied with the power and durability that we put the head into production."
23- Vs. 18-Degree Heads
Granted, high-end 18-degree heads have become much more affordable in recent years, but many people still prefer the simplicity of a more conventional top-end package. "Typically these enthusiasts already have 355- or 383ci engines and want to step up to a 406 or 427, but want to retain their 23-degree-style rocker arms, intake manifolds, and headers," says Noe. To suit these applications, Trick Flow developed its Super 23 Race CNC 230 head. According to Noe, it is ideal for large-cubic-inch engines, retains the stock port location, and will come darn close to making the power of an engine equipped with 18-degree heads. "Right out of the box, these castings made 640 hp on our 11.5:1-compression 406 dyno mule with a 260/270-at-0.050 solid-roller cam. In our opinion, for an application that needs a large port and large runner with a projected output between 500 and 700 hp naturally aspirated, the Super 23 CNC head is the best bang-for-the-buck product, hands down. It's probably as close to an as-cast, 18-degree head as you can get in a standard 23-degree configuration."
New LT1 Heads
Although aftermarket parts development for the Gen II small-block has somewhat stalled in recent years, Trick Flow hasn't forgotten about the LT1 crowd. The company introduced its first LT1 castings in 2004, but has recently revised the design based largely on customer input. "Making a small-chamber LT1 head flow well was a challenge, and with the standard 23-degree valve angle, we were not able to meet our performance objectives. As a result, we rolled the valve angle 2 degrees, which allowed us to run a stock-sized chamber without cutting into the valve seat when decking the head," Noe explains. "Rolling the valve angle also helped us achieve our airflow and power targets. Additionally, we port-matched the intake entry so it precisely lines up with the doweled location of the LT1 intake gasket. Overall, it is an excellent design that will easily make in excess of 500 hp with a mild hydraulic cam."