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AFR 205 vs TFS Twisted Wedge Cylinder Heads - Ultimate Cylinder Head Shootout, The Sequel
It's AFR 205 vs. TFS' new CNC-ported Twisted Wedge heads in another epic airflow battle.
It's really amazing that new products continue to emerge for the gone-but-not-forgotten 5-liter Ford V-8. Here we are, a full decade into the modular Mustang era, and manufacturers are still hard at work cranking out not only continuation products that have been produced since the introduction of the 5.0, but brand-new ones. That companies continue to manufacture and actually develop new stuff for the 5.0 is proof positive the foundation that started an entire industry is alive and well.
One of the recent additions to the ever-growing list of 5-liter components comes from one of the originals, Trick Flow Specialties (TFS). The company's name is long recognized in the 5-liter aftermarket, having not only introduced one of the first aluminum performance heads for the small-block Ford, but it followed up by offering the first affordable aluminum head.
The TFS Twisted Wedge heads all but revolutionized the 5-liter market by bringing a true bolt-on performance head into the hands of the average enthusiast. As we know, TFS went on to increase the offerings, bringing us the amazing TFS R heads, reintroducing the legendary High-Port heads, along with a whole series of performance intake manifolds.
In truth, TFS' most recent offering is not so much a brand-new product as it is an improvement on an existing one. The TFS Twisted Wedge Heads have been with us for some time now and have provided the motivation for literally thousands of Mustangs. Impressive even in as-cast form, these heads provided significant gains over the production cast-iron E7TE 5.0 heads. While the Twisted Wedge heads have proven themselves capable per-formers, there are always enthusiasts looking for more power. Sure, it's possible to step up to the TFS R heads, but a great many enthusiasts are looking to combine the performance of the R head with the true bolt-on simplicity of the Twisted Wedge.
For these enthusiasts, TFS has introduced a CNC-ported version of the TFS Twisted Wedge casting. Looking strictly at the numbers, we see that the 205cc casting tested here stepped up the intake airflow from roughly 245 cfm at 0.600 lift to 316 cfm. Obviously, a gain of 71 cfm is always welcome, but the real key to the success of any street (or strip) head is the all-important average airflow. Combine the average airflow gains throughout the usable lift range (numbers at 0.800 lift are meaningless if you run a 0.550-lift cam) with minimizing material removal (meaning as small a port volume as possible) and you have the makings of a real winner.
Loyal readers will remember the as-cast TFS Twisted Wedge heads performed very well in our Ultimate Guide to Cylinder Heads (Oct. and Nov. '03) Not surprisingly, many enthusiasts have taken steps to improve the as-cast performance offered by the Twisted Wedge heads. Head porting (when performed properly) can greatly improve the flow rate of the cylinder heads, and porters (such as Total Engine Airflow) have been working on the TFS Twisted Wedge heads almost since their introduction. Recognizing the potential for a proper CNC program applied to their already impressive Twisted Wedge heads, TFS decided to step into the CNC market. Rather than just providing the raw materials in the form of their as-cast heads, why not provide the finished product?
Who better to provide the ultimate CNC-ported version than people who designed the head in the first place? While our testing centers on the TFS Twisted Wedge heads (more specifically the 205cc version), TFS also offers a CNC-ported version of the majority of its offerings, including the company's reintroduced High-Port heads and the extremely powerful TFS R heads. You will remember that we recently tested the 185cc heads (against the as-cast version) on a 331 stroker, with excellent results. After seeing the power gains offered by the 185cc heads on that mild application, we couldn't wait to see how well the 205cc heads performed on a larger 408 stroker.
Rather than test the new 205cc CNC-ported TFS heads against their as-cast counterparts, we decided to get serious and pit them against what is certainly one of the top-performing 205cc heads available. We can't swear to it, but we'd venture to guess the AFR 205s represented the performance target for the new CNC-ported TFS heads, and for good reason. The AFR 205 heads have proven powerful in our Ultimate Guide to Cylinder heads and on a number of performance buildups. In the tale of the tape (see airflow data), both heads offered over 300 cfm on the intake and over 230 cfm on the exhaust. The new CNC-ported TFS heads offered more intake flow through the mid-lifts right through 0.600 lift.
It should be noted that the intake airflow gains offered by the TFS heads came with a smaller intake valve (2.02 for the TFS vs. 2.08 for the AFR). On the exhaust side, the AFR heads outperformed the much smaller TFS heads, especially in the mid-lift. According to the data supplied by TFS and AFR, both heads flowed 231 cfm at 0.600 lift. While everyone talks about the big flow numbers achieved at peak lifts, the reality is that the mid-lift flow is every bit as important. This is especially the case when you run a cam that doesn't ever see 0.600 lift.
While the airflow data suggests a serious slugfest between the two heads, we decided to take things to the next level by actually putting them in the ring. To properly test them, we put together a 408 stroker designed for performance street (as opposed to race) use. In fact, this 408 short-block was the same one used on the Windsor/Cleveland hybrid story a couple issues back (Apr. '06).
After removing the Cleveland heads, we shipped the Windsor short-block back to Coast High Performance. Out came the rods and Cleveland-specific pistons and in went a set of its off-the-shelf forged pistons designed to allow us to run both inline (AFR) and offset (Twisted Wedge) valve layouts. Rather than the high-compression flat-tops used on the Windsor/ Cleveland hybrid, we chose a set of dished (19.3cc) pistons that when combined with the 61cc chambers on both our heads, produced a static compression ratio of 10.2:1.
Once completed, the CHP short-block was equipped with a Milodon oil pan, ARP head studs, and Fel-Pro (1011-2) head gaskets. Naturally, the heads were mocked in place to establish the correct pushrod lengths (they are different). The use of an early (non-roller) block required a small base-circle cam. Comp supplied an Xtreme Energy hydraulic roller profile (PN 35-425-8) that provided 0.513/0.529 lift, 230/236 duration split, and a 110-degree lobe separation angle. In retrospect, a wilder cam profile may have been more appropriate to take full advantage of the available head flow.
The 408 was configured for testing with an MSD distributor. The advance curve on the distributor was locked out to ensure both heads were given identical ignition timing. We also installed a ported (by Keith Wilson) Edelbrock Super Victor intake and Barry Grant 850 Mighty Demon carb. Naturally, jetting and timing were optimized to produce the best power curves on the 91-octane fuel. In the end, both heads worked best with 33 degrees of total timing and the same jetting (not surprising given the power curves). Equipped with the AFR 205 heads, the 408 produced 522 hp at 5,800 rpm and 509 lb-ft of torque at 5,000 rpm. The stroker motor was very repeatable, as we made sure to maintain the same starting water temps in the motor.
After swapping over to the new CNC-ported TFS heads, the peak power jumped slightly to 528 hp (at 5,900 rpm), though the peak torque remained at 509 lb-ft at 4,900 rpm. Given the airflow numbers, we expected the power curves to be similar. Apparently the extra intake airflow offered by the TFS heads outweighed the extra exhaust flow offered by the AFR heads, as the TFS heads seemed to pull a little stronger at the top of the rev range.
The popularity of the original Twisted Wedge heads would be difficult to duplicate, but it is nice to know you can get some serious performance from the guys who revolutionized the 5-liter cylinder-head market.
|Tale Of The Tape-Head Flow (Provided By Manufacturers)|