Cylinder Head Testing - LS2 Dyno Thrash Part II: Head Shootout

Air Flow Research (AFR) is a powerhouse in the aftermarket cylinder head business. They offer a wide range of heads that come to the end user with an outstanding reputation for making great power. Their LS1 Mongoose (prepared for this test to run on an LS2 engine) is no exception. The 2.02/1.60-inch intake/exhaust valve arrangement combines with a 205 cc intake port for a delicious combination of high velocity and big flow. Described as "the ultimate street LS1/LS6 aluminum cylinder head," the AFR Mongoose offers a small port that promotes high velocity flow rates for outstanding low lift performance with all of the top end volume that you'd expect in a big-block head. AFR describes its head as "ideal for normally aspirated 346 ci to 396 ci, and it is available with 66 cc and 76 cc combustion chambers. Structural features like Air Flow Research's trademark .75-inch thick head deck, a must for blown and nitrous applications, reinforced rocker stud bosses, and thick wall runners provide unparalleled durability. An exclusive new modern combustion chamber design with double quench pad area helps the LS1 generate huge low and mid lift airflow numbers."On the flow bench, the AFR offered outstanding low lift numbers, especially at .200, .300, and .400 inches of valve lift. Those numbers result in a very torque-rich engine that has a lot of grunt. Of course, with a factory CNC port job, the top end numbers are right there as well--only bested by the TFS head. And, as you'll read, the TFS pieces looked to be custom, hand-ported samples. With the LS2 on the engine dyno and the AFR heads bolted down, our engine cranked out a peak horsepower rating of 547.1 at 6,400 rpm. Stop for a minute and appreciate how much power this is from "just a small-block." At 4,000 rpm, the AFR heads let the LS2 just explode with power, and the torque is right there to move a heavy project vehicle--like a modified Trail Blazer SS.

AFR makes no excuses: they expected to crush the competition. They didn't, but they sure didn't disappoint us. With the aftermarket cylinder head business being so competitive these days, companies are constantly raising the bar. AFR was one of the first companies to offer CNC porting on their own heads in-house, a feature that quickly established AFR as one of the premier head companies in the world. We can easily recommend the AFR head for anyone looking to push their LS2 into some very lofty horsepower territory. The AFR heads will work over a stock head and make most other castings look silly. And, we have a sneaking suspicion that the AFR heads will only get better the harder you ask them to perform, big-inch or power-adder style.