AFR 205 vs TFS Twisted Wedge Cylinder Heads - Ultimate Cylinder Head Shootout, The Sequel

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.