After a thorough engine cooldown, we got to work swapping intakes. Having grown accustomed to the look of the tunnel-ram, a single four-barrel just seemed modest by comparison. Once bolted down, the Holley 950 was mounted, the linkage was connected and adjusted, and the beast was fired. We adjusted the idle and made our first partial pull to determine how far off the fuel mixture was. It looked good enough to pull all the way to 7,000 rpm. The air/fuel ratios were right on the money. No tweaking, no tuning, no jetting, no nothing. Out of the box, the Holley proved lethal. We cooled the Barracuda down and pulled it to 7,300 rpm. We were rewarded with just under 513 hp at the rear wheels. This Indy/Holley combination was proving very effective. We performed a backup pull to make sure the 513 horses weren't a fluke and were handed another 513 hp ticket. No controversy here.
What We learnedWell-designed tunnel-rams work. They make big torque and horsepower everywhere and carry the torque a great distance. You will notice by the dyno charts that the ram produced prodigious amounts of torque and horsepower well past 7,000 rpm, while the single-plane dropped off rather rapidly past its peak of 7,000 rpm. The ram usefully extends the powerband of the engine, enabling you to run a numerically higher gear than you would be able to with a single four-barrel induction. But the tunnel-ram comes with a price. The initial outlay will be significantly greater as the intakes typically cost more, two carburetors must be used, and the necessary linkage must be obtained. Then there's the tuning effort needed to make the system work properly. Do not expect to bolt on a tunnel-ram, set the idle, and go. Considerable toil went into making all of the essential adjustments to the carburetion for the correct fuel metering particularly at high rpm where tuning is even more critical. Then there's the hood clearance issue. The tunnel-ram will more than likely not fit under any stock hood.
As far as the Indy manifold is concerned, we were surprised to find a four-barrel intake that came as close to the output of the tunnel-ram as this one did. Indy certainly did its homework when it produced this clean-slate design. For sheer user-friendliness, look no further than the Indy manifold. We bolted this induction on and laid down well over 500 hp at the wheels. It doesn't get any simpler. Hood clearance with anything more than a 1-inch filter element may be a problem, but the packaging is much more user-friendly than it was with the ram. Indy Cylinder Heads has produced a winner. Not only did it keep the tunnel-ram in sight, it proved much less complex to set up. With the Indy intake, you don't need an expert tuner to get you dialed in. Just bolt it on, make big power and go. For many, that's good enough.
Tunnel-Ram TrendsThe advent of big (large port volume) aftermarket cylinder heads for unlimited racing classes created the need for new-age tunnel-ram designs. How do the modern units differ from the rams of old? Glad you asked. Old-style rams were designed to run at rpm levels typical of the day with available production cylinder heads, which had port volumes a great deal smaller than many of today's aftermarket cylinder heads. The old rams were tall and had long runners that promoted low-end torque. The trend today is for shorter, fatter, tapered runners designed to promote high-rpm horsepower. Tunnel-ram manifold technology has evolved to address this high-rpm need, with vastly improved cylinder heads, cams, and lightweight valvetrains.