AFR Small-Block Heads - Calculatus Eliminatus

Naturally the intake port shape was altered to maximize efficiency.

In addition to the springs, retainers and keeper upgrades, the new AFR Eliminator heads also received new intake and exhaust valves. The key to the weight savings in the new valves was the use of 8mm steams (again, a la LS1) in place of the conventional 11/32ths valve stems. The valve stem upgraded netted 15 grams on the intake, while the exhaust valve weight was actually as wash (both checked in at 99 grams). The reason the new exhaust valve did not net any weight savings was that in addition to the 8mm stems, the valve upgraded also included a tulip head design with an undercut stem. The thicker valve head means improved valve life, but more importantly it means a significant improvement in flow. Remember, reduced valvetrain mass was only one of the goals, and the valve upgrade applied to the new Eliminator heads also improved flow.

The success of the new valvetrain upgrades can be seen in the supplied power curve, as the original AFR heads were run with a 145 lbs seat/315 lbs open spring package against the new Eliminator heads 135 lbs seat/320 lbs open. Despite slightly less spring pressure, the motor was able to run several hundred rpm higher before experiencing valve float.

The valvetrain upgrades would have been a worthwhile upgrade all by themselves, but Tony and the gang were just getting started. Naturally the trend to improving flow is to make the port bigger, but Tony is a huge proponent of maximizing airflow while minimizing port volumes. Port volume is a critical element is driveability (part-throttle response), not to mention average power production (throughout the rev range). Given the AFR lineup was available in a variety of different port volumes, Tony set out to improve the efficiency of the existing ports without resorting to increased volume.

The new Eliminator heads also received valve upgrades. The new valve not only offered undercut stems, but (more importantly) 8mm stems. Dropping down from the conventional 11/32nds stems to the smaller 8mm stems (stem size shared with the LS1 heads) on the intake valves knocked off another 15 grams.

The new Eliminator heads also received valve upgrades. The new valve not only offered unde

While computer simulation and modeling are currently all the rage, the new Eliminator head ports and chambers were designed the old fashion way-with porting tools and a flow bench. Using his experience and knowledge base, Tony worked his porting magic on the Eliminator heads to the tune of an extra 23 cfm, upping the AFR 195 street heads from 262 cfm (at .600 lift) to 285 cfm. The higher-performance Competition package 195 heads were also improved, from 282 cfm to 300 cfm. Note that the new Eliminator street heads now outflowed the previous Competition version.

In true Calculatus Eliminatus fashion, the flow improvements came not from one area, but from eliminating tiny little restrictions everywhere, including the bowl, port and chamber. Even more impressive is the fact that the new Eliminator heads offer flow improvements at every lift value, not just at the peak.

While our testing here was on the most popular 195 cc heads, the Eliminator program was applied to the entire line up of AFR heads, from the street-oriented 180cc heads all the way up to the massive 220cc versions. Though work is still being completed on the larger heads, look for flow numbers approaching 320 cfm numbers from the 220cc heads. While the 210cc and 220cc heads will work well on high-horsepower and large-displacement stroker applications, enthusiasts with stock-displacement 350 c.i. performance street motors might do well to take a look at the new 180cc Eliminator heads.

AFR's Tony Mamo left no stone unturned in his search for additional airflow. The combustion chamber received a great deal of work, as it is a critical element in the quest for power. As with the previous AFR heads, the Eliminator heads will be made available in 64 and 76cc chambers.

AFR's Tony Mamo left no stone unturned in his search for additional airflow. The combustio

Offering 275 cfm at .600 lift, the 180cc Eliminator heads now outflow the original 195cc heads-making for an impressive package. Remember, the best head offers maximum flow with minimal port volume, and the 180cc Eliminator head combines just that. Given the flow rate, we know the 180cc Eliminator head will easily support over 500 hp, yet offer impressive part-throttle response and a broad torque curve. If that doesn't sound like the ideal street motor, maybe we're in the wrong business.

In most instances, yours truly is at the helm when it comes to dyno time, but for this test we relied on the engine experts at American Speed. With a number of impressive small-block combinations to choose from, they had no shortage of test motors for the new AFR Eliminator heads. Given the impressive flow numbers offered by the new Eliminator profile, American Speed chose a 383 stroker to properly illustrate their power potential. The 383 test motor was configured with 9.6:1 compression, a hydraulic roller profile from Comp Cams that offered a 236/242 duration split. The 383 stroker also featured an Edelbrock Performer RPM Air Gap intake, 750 cfm Holley carb and Hooker long-tube headers. MSD supplied the ignition, which American Speed used to dial in 37 degrees of total timing (38 degrees with the original AFR 195 heads).

Running 15W-40 Lucas oil and 93-octane pump gas, the 383 produced 504 hp and 521 lbs-ft of torque with the original AFR 195 (street) heads. After swapping on the new 195cc Eliminator (street) heads, the peak power numbers jumped to 540 hp and 541 lbs-ft of torque. Out near redline, the valvetrain improvements allowed an additional 400 rpm (note on the graph how the original power curve fell off dramatically after 6000 rpm). Judging by these results, we'd say Calculatus Eliminatus was a smashing success.