It is safe to say the original, as-cast Twisted Wedge street head from Trick Flow Specialties (TFS)-now called Twisted Wedge Track Heat 170 Cylinder Head Fast As-Cast-all but revolutionized the Ford 5.0L industry, providing an affordable aluminum performance head to the Mustang market when no such animal existed. The as-cast port dimensions (170cc intake and 66cc exhaust) generated peak intake flow near 250 cfm and peak exhaust flow of 193 cfm (at a 4.150 bore, larger than our 347's 4.030), and the rotated valve locations not only improved the flow and power potential but also the all-important piston-to-valve clearance issues associated with running wilder cams with the factory pistons. According to TFS, it is possible to run cams with as much as 0.540 lift and 224 degrees of duration using the stock flat-top pistons, despite the use of larger 2.02-inch intake valves (stock 5.0L heads relied on a 1.74/1.46 valve combo). And let's not forget that the Twisted Wedge street heads achieved full 50-state emissions status for 1996-and-earlier 289, 302, and 351W Fords.
The right set of 5.0L heads can make all the difference in the world, or at least an extra 36 hp.
While the 5.0L crowd embraced the Twisted Wedge design, time, technology, and the competition marched on. To keep pace with the more than 30 different aftermarket small Ford heads, TFS has applied CNC porting to its already impressive Track Heat Heads (as well as its original High Port and R-series heads).
The test motor consisted of a 347 short-block from Coast High Performance that uses a forged crank, rods, and flat-top pistons. We also installed Fel-Pro 1011-2 head gaskets and 7/16-inch ARP head studs.
The test seen here involves a comparison of the latest Fast As-Cast Twisted Wedge Track Heat 170 heads and the CNC-ported Track Heat 185 heads. This will help you decide if the up-price for CNC porting is worth it for your small-block Ford project. The As-Cast heads cost $1,249 per pair and the CNC-ported versions are $1,759 from Summit Racing.
The intake port volume increase of 15 cc, along with the CNC port shaping, netted a gain of 50 cfm, upping the peak flow figures (at 0.600 lift) from 251 cfm on the As-Cast head to 301 cfm. Thus, a 9 percent increase in port volume netted a 20 percent jump in peak airflow. Even from an average airflow standpoint (tested from 0.100 lift to 0.600 lift), the porting improved the average flow rate by nearly 11 percent. Even more impressive is the fact that these gains came with no change in valve sizing. Gains of this magnitude came from extensive work on the airflow bench and dyno, as man does not live by flow numbers alone.
To properly test the merits of the CNC-ported heads, we assembled a 347 test motor. The short-block came from Coast High Performance and featured a 3.4-inch stroker crank, forged-steel rods, and aluminum flat-top pistons. The Probe Racing pistons featured dedicated valve reliefs for the Twisted Wedge valve orientation. The short-block was stuffed with a TFS Stage 3 hydraulic roller cam that offered a 0.574/0.595 lift split, a 236/248 duration split (at 0.050), and a 110-degree lobe-separation angle. The 347 was also equipped with a full Milodon oiling system, including pump, windage tray, and oil pan. Fel-Pro supplied the 1011-2 head gaskets that we secured with ARP head studs. Topping the long-block was an Edelbrock Performer RPM Air-Gap intake and Holley 750 HP carburetor. Both heads were run with a set of 1.6:1-ratio TFS roller rockers and 1 3/4-inch Hooker Super Comp headers feeding 18-inch collector extensions (no mufflers). Prior to running, the motor was treated to a 20-minute, computer-controlled break-in procedure using Lucas 5W-30 conventional oil.
Run with the FAST As-Cast 170 heads, the 347 produced peak numbers of 455 hp and 416 lb-ft. The numbers jumped to 482 hp and 424 lb-ft once we installed the CNC-ported heads. Making these power gains even more impressive was the fact that the ported heads featured CNC-shaped combustion chambers, which actually lowered the compression ratio by 3/10 of a point. In Trick Flow's own testing on a slightly more powerful 347 combination, the 185 heads were worth as much as 40 hp.
Airflow Data: Fast As-Cast Vs. CNC-Ported TFS TW Lift Intake Exhaust CAST CNC CAST CNC 0.100 63 70 53 56 0.200 141 146 107 112 0.300 205 216 144 150 0.400 233 258 171 192 0.500 251 287 187 220 0.600 251 301 193 231Note: Flow numbers are with a 4.150-inch bore and with a flow tube on the exhaust.
TFS Twisted Wedge Head Test: As-Cast vs. CNC-Ported
The CNC porting not only improved the peak power output, but the additional airflow raised the power throughout the rpm range. A sure sign the R&D department at Trick Flow Specialties understands it takes more than just bigger to make it better: The 185cc ported heads picked up power down at 3,000 rpm on this combination. The optimum port is one that maximizes flow while minimizing port volume. The CNC heads improved the power output of the 347 by as much as 36 hp over the already powerful FAST As-Cast 170 heads. Had the CNC heads been milled to replicate the compression ratio of the as-cast heads, the gains would have been even more substantial. The airflow offered by the CNC-ported heads will support more than 600 hp on the right combination.
