While the power formula can be used as a guide, the reality is that the eventual power output of any motor is not solely determined by the flow rate of the intake port on the cylinder head. It should come as no surprise that adding these Pro 1 CNC heads to your stock 302 would never result in over 600 hp. The remainder of the combination (displacement, cam, and compres-sion) will obviously affect the power output as will the exhaust flow, carburetion, and even header configuration. Suppose you had a head that offered big-time intake flow but suffered with a poor exhaust-port design. You can't expect that head to offer as much power potential with a poor exhaust port regardless of the intake flow (though cam timing can be used to offset some of the disparity). With 235-cfm exhaust ports, the Pro 1 heads offered an impressive 72 percent intake-to-exhaust flow relationship, so the exhaust ports wouldn't hold the power potential back on these heads. It's important to note that we have on occasion exceeded the power output suggested by the airflow formula, but this is usually the exception rather than the rule.
Using the 1.6 ratio Crane Gold rockers, we checked for both piston-to-valve clearance and the necessary pushrod length with our Dart heads and roller cam combination.
At MM&FF, we would never simply provide our readers with airflow numbers and call it a day. Knowing how our readers live and breathe for dyno numbers, we decided to see just how close we could get to the numbers suggested by the power formula. Since we went looking for something over 600 hp, we decided to build a motor capable of utilizing every bit of airflow offered by the new Dart Pro 1 heads. Our Pro Street Stroker short-block came from Coast High Performance. The CHP stroker features a 351 Windsor block stuffed to the gills with a 4.0-inch stroker crank. When combined with a 0.030-inch overbore, this upped the displacement from the standard 351 ci to a full 408 cubes.
The big-inch Windsor featured 11.7:1 compression thanks to a set of forged flat-top pistons and connecting rods from Probe Racing. Exceeding 600 hp requires a healthy cam profile, so we went right to the experts at Comp Cams for a solid roller profile. The cam for our Pro Street Stroker featured 0.688 intake lift, 0.672 exhaust lift, and a 264/268 duration split at 0.050. The aggressive roller cam also featured a tight 106-degree lobe-separation angle. The Dart heads were topped off with a ported Edelbrock Super Victor intake and a 950 HP Holley carburetor. Also present was a set of Hooker Super Comp headers, an MSD ignition, and a CSI electric water pump.
After installing the heads using Fel-Pro 1011-2 head gaskets and 1/2-inch ARP head studs, we installed the intake and carb and warmed up the 408-inch beast on the Westech Superflow engine dyno. After bringing the motor up to temperature, we gave it a full 30 minutes of break-in time before subjecting it to full throttle loads.
We then changed out the conventional oil used during the break-in procedure for Lucas Synthetic 5W-30. The preliminary loads at 4,000 rpm looked promising, as the 408 thumped out over 500 lb-ft of torque. After some jetting and timing sweeps, we were finally rewarded with some big numbers, as the Dart-headed 408 produced peak power numbers of 618 hp at 6,600 rpm and 562 lb-ft of torque at 5,100 rpm. Torque production from the big Windsor exceeded 550 lb-ft from 4,600 rpm to 5,700 rpm, and exceeded 500 lb-ft from 4,000 rpm (or lower) all the way to 6,500 rpm. Though we failed to reach the potential power output suggested by the power formula, we suspect that a larger carb would have helped (there was vacuum present at W.O.T.) as would a larger set of Hooker headers. An oil pan with additional windage control would surely improve power as well, but all in all, we were plenty pleased with our 618hp Pro Street stroker.
Topping the Dart heads was an Edelbrock Super Victor intake ported by Keith Wilson. | 
Running a set of 1-3/4-inch Hooker headers, the 408 Pro Street Stroker produced 618 hp and 562 lb-ft of torque. Like the carb, we think larger headers may have improved power as well on this 408. | 
Holley supplied the necessary carburetion for our dyno test in the form of a 950 HP. In retrospect, we should've opted for one of Holley's larger 1050 Dominators as there was vacuum present in the manifold at wide-open throttle. |