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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.
We headed to Steve LaPointe Race Engines to see what the Twisted Wedge Two-Valve heads would do on a flow bench. LaPointe used the same bore size as our test engine (3.552-inches) to ensure accurate results. The heads peaked at 0.600-inch lift with 253 cfm for the intake side and 189 cfm for the exhaust. That compares to 219 cfm (intake) and 200 cfm (exhaust) for the CNC-ported stock heads, but the head is more than just a set of healthy flowing ports and a nice combustion chamber; Trick Flow addressed many issues.
The new Twisted Wedge modular heads accept both Windsor and Romeo style valve covers, which makes ordering them easier as enthusiasts sometimes mix up the names and styles. The spark plug holes accept a traditional style plug with a full 3/4-inch reach to eliminate blowouts and the need for inserts. We used NGK TR6 4177 spark plugs (one range colder than stock) with a 0.035-inch gap for this test. The deck of the head is also 3/4-inch thick, to help prevent the cylinder head from lifting in high-boost and high-compression applications.
"The Twisted Wedge Two-Valve heads are the only 1.840-inch intake valve heads on the market that you can bolt onto a stock bore/piston short-block. All other 1.840-valve heads require a 0.020-inch overbore so the valves clear," notes Noe.
"We talked to NMRA racers and shops and kept hearing complaints about the cam journal oiling at high rpm," said Noe. TFS addressed the concerns with a new oiling system that better feeds the cam journals at high rpm levels. The journals are removable and the four-bolt pieces are made from a powered metal. Noe notes, "There is a specific reason we use a proprietary powered metal for the cam journals." It centers on durability and manufacturing but that is all he would say on the patented setup.
Putting the Twisted Wedge Heads to the Test
Our test vehicle is a '00 Mustang GT out of the Dez Racing shop (Seekonk, Massachusetts), and the Two-Valve combination starts with a stock engine block that was bored 0.020 to 3.552 inches. A new cast-steel crank with a stock 3.550-inch stroke swings eight H-beam steel connecting rods and forged pistons. The stock cylinder heads feature a Stage 2 CNC port job from Total Engine Airflow, and are topped off with a pair of F-42 camshafts from Anderson Ford Motorsport. ATI's P-1SC centrifugal supercharger pumps 11-12 psi of boost into the Fox Lake P-51 intake manifold.
The exhaust is rather small with a set of Ford Racing shorty headers connected to a Bassani 2.5-inch x-style midpipe and after-cat exhaust. Without methanol injection, the '00 Stang made 466 rwhp and 429 rwtq with 17 degrees of ignition timing and 93-octane pump gas. Our baseline pull with the Snow Performance water/methanol kit spraying down the intake charge showed 486 rwhp and 447 rwtq-the increase due to the 23 degrees of timing that the meth injection allowed. All dyno testing was performed on a DynoJet chassis dyno and the car features a Tremec T45 five-speed manual transmission.
The engine uses a set of ARP head studs, making a head swap with the engine in the car difficult, if not impossible. Brian Machie of Dez Racing yanked the mod motor to make things easier-as crazy as that might sound. He had the engine out in less than two hours, and took off the top-end shortly after that. The heads bolted on just fine and we used a set of Fel-Pro Multi-Layer gaskets (0.036-inch thick). Our compression ratio increased from 9.1:1 to 10.4:1, thanks to the 38cc chamber of the Twisted Wedge Street/Strip head. Our stock CNC-ported heads had a 44cc chamber and Ford delivers stock P.I. heads with a 38cc chamber. Moving down to the non-P.I. heads, the combustion chamber goes to 52 cc.
We left the pulley sizes identical, so the blower delivers the same amount of airflow to the engine. That would give us a true indication of how much more power these heads make over our CNC-ported stock ones. On the dyno, Mike Dezotell of Dez Racing started conservatively by backing the timing down from 17 degrees to 13 degrees. He was concerned with the higher compression and pump gas. A few dyno pulls and the results were 483 rwhp and 439 rwtq.
"It wants more timing," commented Dez as he fiddled away on the SCT program. He gave it just that and set it at the same 17 degrees as our baseline pull. The result was an outstanding 499 rwhp and 462 rwtq, which work out to gains of 34 rwhp and 33 rwtq over our baseline pulls.
Our 499/462 performance was backed up with a near identical 499/461, showing our results weren't bogus. Dez then swapped the program over to one for the Snow kit. He kept the tune identical; we were just increasing timing due to the better octane rating the meth delivers. The same baseline 23 degrees and air/fuel ratio provided us with an additional gain of 15 rwhp and 16 rwtq, for a grand total of 514 rwhp and 477 rwtq.
"That is the most power I have made with a P-1SC supercharged car. Typically, a combo like this with bone stock heads will make 435 rwhp and 465 or so with CNC-ported stock heads. The Trick Flow heads are 60-65 rwhp better than unported stock heads," claimed Dezotell.
Interestingly, the boost remained at 11-12 psi throughout all of the tests, despite the better flowing Twisted Wedge Street/Strip heads. Some might wonder why the boost stayed up, and our best assumption is the increase in compression ratio.
"We are only scratching the surface with these heads. I think larger cams, like the Anderson Ford Motorsport F-72 ones, springs to match, and a better exhaust system will allow us to pull higher rpm levels for even better gains. As we work more with these heads, the more we will know what it likes. I have seven pairs of Trick Flow heads ordered for customers, so we should know soon enough," commented Dez.
For now, simply bolting the Trick Flow Specialties Twisted Wedge Street/Strip Two-Valve heads on top of a mildly supercharged mod motor proved to be worth 34 rwhp. Four-Valve and Three-Valve mod motor combinations are going to have some fast company from its little Two-Valve brother. Let the mod motor games begin!
Flow Bench Notes
- Bore Size: 3.552
- 28 inches of water
- Trick Flow heads feature 1.84/1.45 valves
- Stock Heads feature 1.78/1.45 valves