Dyno Duel

We gave you a look at Trick Flow Specialties' new 18 degree race cylinder heads for small block Chevy ("18 Degrees of Horsepower"). While we were doing that article, the Trick Flow guys were getting ready to dyno test a new small block aluminum head, this one aimed at the street/strip crowd. Being the nosy types that we are, we stuck around to see what these heads were all about.(Image 1)

Trick Flow calls them 23 Degree Street Heads, so named for the conventional 23 degree valve angle. But what they lack in fancy name, they make up in performance. The 23 Degree is a direct factory replacement piece, designed to give the average street shoe an aluminum head for about the same price as a set of good cast iron heads. But as you'll see, the 23 Degree makes more than factory replacement power.

Trick Flow could have dyno tested the 23 Degree against some weak-kneed factory iron head and gotten some outrageous numbers. But instead, they squared off against the fabled Corvette L98 aluminum heads. Call it the duel of the direct replacement heads; both the 23 Degree and the L98 are bolt-on swaps for stock iron heads, and are very close price-wise. But when it comes to power, the dyno tells a very different tale.

The test engine was a 383 cubic inch small block (.030 overbore, 3.750" stroke crank, 5.700" rod) with a 230°/236° (at .050) duration Comp Cams hydraulic roller cam, and an Edelbrock Victor Jr. intake with a 750 cfm Holley double pumper--just like the ones Mom used to build. Both the 23 Degree and the L98 heads were run in out-of-the-box condition with Trick Flow 1.5 ratio roller rocker arms.

Trick Flow also did some comparison testing of two sets of cast iron heads--the World Products Sportsman II and the Dart Iron Eagle. The results proved very interesting, as you'll see in "Iron Men". For now, let's see how our aluminum heads stack up--and what the Superflow dyno has to say.

So how did our dyno duel end? As Superflow results show, the L98s peaked at 420 horsepower at 5,500 rpm, with torque maxing out at 440 foot-pounds at 4,000 rpm. While the L98s made marginally more power under four grand, the 23 Degree's better port design and bigger valves left the GM heads in the dust from 4,500 rpm on up. The Trick Flow heads kept pulling through 6,000 rpm, where they peaked at 460 horsepower. Torque maxed out at 451 foot-pounds at 5,000 rpm.

So which one to choose? If you have to have factory stuff, get the L98s. But for about the same price, the Trick Flow 23 Degree heads offer more horsepower, more torque, a broader rpm range, and are just as easy to bolt on as their factory competitors. In our humble opinion, the Trick Flow heads are a better deal.

The line forms to the right.

Test Engine Specifications

Small block Chevy, 383 cubic inches
10.1:1 (Trick Flow heads), 10.8:1 (L98 heads)
Trick Flow 3.750" forged crank and 5.7" forged rods, Keith Black hypereutectic pistons with -12cc dish
Comp Cams hydraulic roller, 230°/236° duration @ .050, .510"/.520" lift
Trick Flow roller, 1.5 ratio
Edelbrock Victor Jr. manifold with Holley 750 cfm double pumper
MSD Billet distributor and 6AL ignition
Hooker 1 3/4" primary headers, 3" dual exhaust with 2-chamber Flowmaster mufflers