Intake Manifold Engine & RPM Range Test - Induction Extravaganza

It seems everyone has a favorite intake manifold. Some guys scour swap meets, garage sales, and dumpsters looking for long discontinued intakes because they know "they're the best." Others are convinced the old 440 Magnum four-barrel iron piece is as good as it gets, although a little heavier than that aluminum aftermarket stuff. Tell them it's the exact same intake used on Grandpa's standard 440 Chrysler New Yorker of the same year, and chances are they'll call you a liar. What's the truth? To some extent, that depends on what you're after. It's said that two-plane intakes produce more power lower in the rpm range, while single-planes offer more power higher in the range, given an engine built for high-rpm performance. I've seen it in enough dyno runs to know it's more than a myth. This is a good place to start, but most people have to rely on past experience. To get some real-world data, we lined up some intakes and ran a dyno test.

Here's a simple piece of engine-building theory to consider: The more power the engine makes, the more critical manifold selection becomes to peak power output. Take a stock big-block and run a comparison on intakes-there may be 15-25 hp between the best and worst. Run the same intakes on a radical drag motor, and the range will broaden dramatically.

Of course, there are considerations other than peak power output when selecting an intake for a specific combo. For instance, factors such as the rpm range and low rpm torque requirements of the application require attention. However, if the goal is to put a selection of intakes through the acid test, the way to do it is to run them on a high-powered engine that will really pull the air. Our objective this time was to test for higher rpm power. We gathered as many 440 intakes as we could get our hands on and did just that.

All the intakes were single four-barrel 4150-flanged designs; and all, with one exception, were run out-of-the-box stock. When custom porting enters the equation, a big variable is thrown into the results. Some intakes naturally benefit from porting or even port matching, but the end user's results also vary depending on who does the port work. While hardcore builders wouldn't consider running a manifold without doing some carving first, the majority of intakes are likely just unwrapped and bolted on. This is exactly what we did here. Note that our high-powered test engine and test rpm range greatly favored the single-plane designs, so all of the single-planes had an advantage.

The Engine
The mule for our test wasn't your ordinary street mill, but rather a stout 440 combo that could use all the intake it could get. The block was .060-inch-over production 440, with Arias-forged 12.5:1 domed pistons, Eagle H-beams, the factory-forged crank, and a Milodon oiling system. The heads were production-915 castings and the ports were seriously reworked with max effort (no welding or epoxy) porting job and fitted with custom Manley 2.25-inch intake valves and 1.81-inch exhausts. Working the valves was a full Competition Cams' cam-and-valvetrain package, including a custom Comp roller, with their NC4149 intake lobe and High Tech .420-inch exhaust lobe. It worked out to 260/258 at .050-inch and over .650-inch lift with Comps 1.6:1 aluminum roller rockers. A Milodon gear drive turned the cam. We called it the "Iron Head Air Hammer."See Mopar Muscle March 1999, May 1999, and Sept. 2001 for more on this engine.

1. Factory Iron circa '70-'71
For our first test, we bolted on a factory #2951736 cast iron intake, the four-barrel intake used on '70 and '71 440s. We'd like to think that no one in their right mind would bolt one of these onto a high compression, big-valved, roller-cammed 440, but we had to start someplace. Even we were surprised to see the numbers we got, although the engine was way off its potential. On stock and mild engines, we've seen meaningful gains easily achieved with aftermarket intakes.