PLATINUM Though the differences between the old and new exhaust ports aren't as striking a
PRO 1 ...the new shaping around the valveguide is evident, as is the CNC work in the bowl.
PLATINUM Dart paid a great deal of attention to the valve-seat area when creating the Pro
PRO 1 ...More importantly, each angle is a shear point, which helps to reintegrate liquid
Dart's wet flow process uses a solvent with the same specific gravity as gasoline. Under a
Q&A WITH TONY MCAFEE OF DART MACHINERY
CHP: How did this redesign start, Tony? Tony McAfee: It was time to upgrade the Iron Eagle and Pro 1 heads, so what we did was take the old design and played with the wet flow process we've been using on our Pro Stock heads, looking to make a better mousetrap.
CHP: What are the advantages of the wet flow process? TM: You're simulating a running engine more closely than on a dry flow bench. An engine doesn't run just on air. When you add fuel, the whole airstream becomes heavier; it does much more than dry air.
CHP: Like what?TM: When you see the fuel run, it runs in streams. You see the vortices in the combustion chamber. And no matter what, fuel attaches to the port walls... It's gonna happen.
CHP: And you can actually see this on the wet flow bench? TM: Yes. It can be seen in black light, through a half port made of clear plastic. You can see everything the mixture does, where it's at, how it moves. We've been able to see many things we couldn't imagine.
CHP: So what have you learned so far? TM: The combustion chamber should be thought of as an extension of the intake port, and the way it's shaped can improve air/fuel distribution around the valve. The plug is also moved toward the exhaust port; it's now in the same place as a Vortec head. Flame travel is one of the big positive sides to a Vortec head. Most people think it's airflow, but that's only half of it.
CHP: What other areas have you found to be important? TM: The cross section of the port, for one. We've also worked on the short turn and the diameter of the throat. They need to be a specific area based on valve size. Also the bowl and valve-seat area. We want it to gather loose fuel, rather than let it hit just the back of the valve. Once it leaves the valves, you have to make the mixture keep moving.
CHP: Once you've seen how the air/fuel mixture acts on the wet flow bench, how do you go about achieving the results you're looking for?TM: It's trial and error, using traditional methods: epoxy, grinding, and welding. We do anything we can do to make it flow better. I'm still trying to teach myself how to influence the mixture flow.
CHP: Really? TM: Wet flow technology is in its infancy. I don't know half of 1 percent of what we'll know in a few years.
|GOING WITH THE FLOW |
|Dry Flow (@ 28 inches of water) |
|Pro 1 215||Pro 1 215 Platinum |
|Lift (inch)||Intake (cfm)||Exhaust (cfm)||Intake (cfm)||Exhaust (cfm) |
|0.200||128.0 ||114.8||144.1||107.0 |
|0.400||230.5||165.8||228.2 ||166.4 |
|0.700||260.9||191.3||268.2 ||199.9 |
|Wet Flow (@ 55 inches of water) |
|Pro 1 215||Pro 1 215 Platinum |
|Lift (inch)||Intake (cfm)||Fuel (lb/hr)||Intake (cfm)||Fuel (lb/hr) |
|383 STROKER SPECS |
|Displacement||384.6 ci |
|Bore x Stroke||4.040 x 3.750 inches |
|Rotating assembly||Speed-O-Motive cast crank and forged rods |
|Pistons||Mahle forged |
|Heads||Dart 215cc, 72cc chamber |
|Intake manifold||Dart single-plane |
|Carburetor||Holley 750-cfm Street HP |
|Distributor||Pertronix Flame-Thrower |
|Camshaft||Comp Cams hydraulic roller |
|Valve lift||0.520/0.540 inch, intake/exhaust |
|w/1.6 rockers||0.555/0.578 inch, intake/exhaust |
|Duration at 0.050||236/248 degrees, intake/exhaust |
|Intake centerline||108 degrees |
|Lobe separation||113 degrees |
|DYNO DETAILS |
|Headers||13/4-inch Hedman long-tubes with 18-inch extensions |
|Fuel||91-octane unleaded |
|Jetting||75 primaries, 80 secondaries |
|Timing||37 degrees |
|Iron Eagle Platinum |
|Max torque||464.2 lb-ft @ 4,600 rpm |
|Max power||463.9 hp @ 5,900 rpm |
|Average torque||425.4 lb-ft |
|Average power||335.8 hp |
|Pro 1 |
|Max torque||473.1 lb-ft @ 4,700 rpm |
|Max power||479.7 hp @ 5,700 rpm |
|Average torque||432.3 lb-ft |
|Average power||342.2 hp |
|Pro 1 Platinum |
|Max torque||483.8 lb-ft @ 5,000 rpm |
|Max power||503.2 hp @ 6,000 rpm |
|Average torque||441.5 lb-ft |
|Average power||351.0 hp |