Muscle Mustangs & Fast FordsHow To Engine
Twisted Wedge Two-Valve Heads - Two-Cam Cylinder-Head Jam
Trick Flow Specialties Two-Valve Heads Turn The SOHC Market Upside Down-We Gain 34 RWHP Over Ported Stock Heads.
When the first modular motor-powered Mustang rolled off the assembly line and on to dealership lots in 1996, it had the same great looks, but the standard V-8 was a Two-Valve mod motor displacing 4.6L. The popular and successful 5.0L pushrod engine made way for a more complex engine with overhead cams, delicate short-blocks, and a new computer system.
For the diehard 5.0L fan, it was a dark time in Mustang history, but the Mustang aftermarket eventually adapted and unlocked the potential within the 4.6L. People quickly realized that the mod motor responds well to boost; it can be made into a snappy engine capable of big power with a short list of mods. While the Two-Valve engine isn't an overly powerful combination in naturally aspirated trim, the cylinder heads are not bad for a factory casting. Many specialty machine shops have ported the stock heads and found decent improvements in flow numbers, but despite being released 14 years ago, the Two-Valve market hasn't benefited from a new aftermarket cylinder head casting-until now.
Over the years, many companies have expressed interest, but always cited manufacturing costs and the fact that ported OEM heads were decent enough for enthusiasts' horsepower desires. That didn't stop Trick Flow Specialties from moving forward on a top-secret project last year.
"We looked at the market and saw the 4.6L Two-Valve segment was neglected. We looked at what we could do there, and many of our dealers were asking us for a Two-Valve cylinder head," commented Al Noe of Trick Flow Specialties (TFS). "We first thought about doing a big port version of the stock head, but there was only so much we could do. It would only be slightly better than stock without any room for improvement." It forced Trick Flow to look at the heads from a different angle.
When the 2008 SEMA show rolled around, the world was introduced to a chunk of aluminum that would change the Two-Valve market. Not only did the company overcome manufacturing concerns (mostly centered around the cam journals) but also performance. "Our goal was to deliver a cylinder head that was 20hp better than fully-ported stock heads currently on the market. We tested several CNC-ported heads to determine a benchmark we had to beat-a head from nearly every CNC shop out there," commented Noe.
It wasn't an easy task, but the company moved outside of the box to improve the performance of the head and incorporate many unique features and benefits. Trickflow's Twisted Wedge Street/Strip cylinder heads for 4.6L Two-Valve engines were designed from a clean sheet of paper.
"We have two patents for this cylinder head. One covers the cam journal design and method of manufacturing; the other is the application of the Twisted Wedge combustion chamber/valve layout," commented Noe. The first highlight TFS noted was the Twisted Wedge combustion chamber, which twists the combustion chamber to benefit airflow into the chamber, as well as aid in piston-to-valve clearance. This twisted chamber is a design utility that was carried over from the company's other heads.
"Our initial plans with a big port version limited the head. But once our engineers flipped the intake valve to other side, we could accomplish a lot of our goals," stated Noe. The flip helped moved the valve away from the cylinder bore, which enhances airflow (especially in the mid-lift range), increases piston-to-valve clearance, and allows for larger valves. Those advantages helped TFS accomplish its 20-plus-horsepower goal over stock ported heads. "We typically see 30-35 hp over ported stock heads," proudly proclaimed Noe.
The intake inlet is styled after the OEM P.I. head, so existing manifolds bolt on and line up properly. From there, the ports take different paths. Both the intake and exhaust ports of the Twisted Wedge head are deemed "Fast as Cast," a Trick Flow Specialties trademarked design where cast ports flow as well as CNC versions. This allows for a smaller price tag than a set of CNC'd heads.