There are literally thousands of aftermarket parts available for our classic Mopars, and a large number of those items are designed to increase engine power. One part that most enthusiasts like to replace themselves is the intake manifold, but with such a variety of intake manifolds on the market it can be difficult to decide which one is correct for your application. This month, we’ll give you some pointers based not just on our years of experience, but on dyno and track results, that will help you decide which style of intake manifold is correct for your Mopar.
Changing the intake manifold is a fairly easy task on most Mopar engines, and can benefit the car in two ways. First, most factory intakes are made of heavy cast-iron, so replacing the stock intake with an aluminum aftermarket piece will certainly shed a considerable amount of weight from the car’s engine. Additionally, the intake can be chosen based on the displacement, power, and rpm range of the engine as well as the car’s weight, rear end ratio, and other parameters to improve the overall performance of the vehicle.
OK, so a tunnel-ram might not be the correct choice for the engine in your Mopar, but how do you choose the right intake? We’ll show you in this month’s Quick Tech.
Intake manifolds can be divided into the categories of dual-plane or single-plane, based on how they are designed. A single-plane intake manifold has an open plenum, allowing all four barrels of the carburetor to feed all the cylinders. A dual-plane, as the name implies, has a split plenum, separated by a divider wall, letting each side of the carb feed four cylinders. As a rule, dual-plane intakes make better low rpm torque, but sacrifice upper rpm horsepower. Single-plane intakes are in a sense opposite, making great high-rpm power while sacrificing torque, or at a minimum moving peak torque to a higher rpm.
In general terms, if your engine has a somewhat stock camshaft and mild compression, or if your car has a highway friendly low gear ratio, automatic transmission, and stock torque converter, a dual plane intake would usually be the best choice. Alternatively, if you drive an A-body with 4.88 gears, a loose converter, high-compression, and big roller camshaft, you’ll no doubt want to consider one of the many single-plane intake manifolds on the market.
Be aware that there are likely several good choices for your car when it comes to the intake manifold. It’s always a good idea to consider all of the vehicle’s variables as well as trusting the judgment of the engine builder to match components properly based on the intended use of your Mopar. And while it’s impossible in these two pages to test every Mopar intake manifold on the market, we will tell you this: All of the aftermarket intakes we’ve tested perform better than the factory intakes they’ve replaced, in addition to being lighter. Need more help deciding which intake is right for your Mopar? Be sure to visit the forums and tech archives on our website, www.moparmusclemagazine.com/techarticles/engines/index.html, for more information on this subject.
1. We’ve tried various types...
1. We’ve tried various types of intake manifolds on virtually every engine produced by Chrysler, in both race and street cars, and on the dyno. While each combination is slightly different, there are some rules of thumb when it comes to choosing intake manifolds.
2. Dual-plane intake manifolds...
2. Dual-plane intake manifolds have a split plenum and divider wall, effectively dividing the carburetor into two separate two-barrels, each feeding four of the eight cylinders. These intakes are best suited for low to mid-range torque, though modern designs don’t sacrifice much in the way of power under 6,000 rpm.
3. Modern dual-plane intakes...
3. Modern dual-plane intakes like the Edelbrock Performer RPM have a portion of the dividing wall cut out, allowing both banks of cylinders to slightly benefit from all four barrels of carburetor. Older dual plane designs can be modified with a grinder to achieve the same results.
4. Single-plane intake manifolds...
4. Single-plane intake manifolds like the Edlebrock Victor series offer a large, open plenum, allowing big displacement engines with aggressive cams to take a deep breath of air and fuel. This style of intake manifold makes power at a higher rpm than a dual-plane intake, and is better suited for race cars or hard-core street cars than it is for mild street cars.
5. Another thing we’ve discovered...
5. Another thing we’ve discovered during our testing is that carburetor spacers generally make additional power and torque, especially in larger displacement engines.
6. So if you have the hood...
6. So if you have the hood clearance, either an open or tapered spacer in addition to the right intake manifold can help your Mopar make even more power.