With their radical-looking Ram Induction setups, Mopars of the early ’60s sported some of the wildest engine compartments ever seen around the Motor City. Here’s what that was all about.

 

 

At your local cruise-in or cars and coffee, you’ve probably seen a few of these wild induction systems under the hoods of some early ’60s Chrysler products. Indeed: At more than four feet wide and boasting a pair of big Carter carburetors, they’re pretty hard to miss. While the setups were relatively rare even when new and produced in their original form for only a few years, the principle behind them is commonplace throughout the auto industry today.

 

Explanations for ram induction theory range from simple to fiendishly complex, so we’ll start with the simple version. In a common four-stroke engine, every time the intake valve slams shut, the air-fuel charge packs up behind it. This occurs because the charge has mass and inertia, and at 6,000 rpm it happens 50 times per second. Each time, a reflecting pressure wave is sent back up the intake passage toward the atmosphere at the speed of sound.

So: If we can adjust the length of the intake passage to the engine’s desired operating rpm, we can pressurize the incoming air-fuel charge by a few significant percent. Thus we can get more air into the cylinders and produce more output. It’s a little bit like supercharging, but without the mechanical losses associated with turning a pump. The tiny chart inset in the illustration above shows how ram induction potentially lifts and fills the engine’s torque curve.

The drawing above also shows, from the inside out, how Chrysler executed the ram principle on production cars. The standard intake manifold was exchanged for a pair of long-tube aluminum castings, one for each bank of the V8 and each one fed by a Carter AFB four-barrel carburetor. Note how the manifold runners are draped over the valve covers for hood clearance, and the balance tube connecting the two manifolds for smoother idle.

 

One visible early example of Chrysler’s experiments with ram tuning was in its A-311 Indianapolis 500 program, above. Eager to promote its new 331 CID hemi V8, the carmaker approached the race sanctioning board in 1951-52 with a proposal to compete in the Indy 500. But when race officials saw the engine’s considerable potential, they scotched that plan. The hemi V8 was welcome, but only at the same 270 cubic-inch displacement as the classic Offenhausers et al. At that point the project was tabled, but the special components and the experience gained in the effort carried on.

The calculations used to determine the length of the intake runners can be as sophisticated as you wish to make them, but after considerable experimentation, Chrysler engineers arrived at a simplified empirical formula: N x L = 84,000, where N is the desired operating rpm and L is the length of the runner in inches. Tuned to optimize for peak torque rpm, the Ram Induction intake runners on Chrysler road cars were 30-31 inches long, and the carmaker claimed an improvement of up to 10 percent.

 

In the late ’50s a group of young Chrysler engineers formed a car club called the Ramchargers, and their first club project, a 1949 Plymouth drag car, made flamboyant use of the company’s ram tuning experience (above). The tall intake manifold was a discarded dynamometer test piece, and the wild exhaust headers also followed Chrysler ram tuning principles. According to noted Chrysler engineer and Ramchargers co-founder Tom Hoover, the headers’ megaphone shape was borrowed from a Norton motorcycle technical paper. Those who witnessed the car’s appearance at the 1959 NHRA Nationals at Detroit Dragway say it was the loudest thing on the property.

 

On production models, Chrysler’s ram induction scheme was offered on 1960-61 Plymouths where it was branded as the Sonoramic Commando, and on 1960-61 Dodges where it was called D-500 Ram Induction. At the premium Chrysler division, the setup was simply called Ram Induction and was offered on the Chrysler 300 letter series cars through 1964 (300K shown above.)

While the various systems are visually similar, there are some detail differences. To improve mixture distribution and cold driveability, exhaust heat and engine coolant circuits (either or both) were added to heat the air/fuel charge. There are both “long ram” and “short ram” manifold versions, which are the same physical exterior length, but in the short ram the paired runners are conjoined for half their length to move the torque peak up the rpm range. While these original Mopar Ram Induction systems were spectacular in appearance, they never caught on in racing applications because they were tuned for peak torque rpm rather than for peak horsepower—great for street performance, but not so great for racing use at max rpm.

 

While the Ram Induction setup was most commonly found on Mopar’s B/RB big-block V8s, it was also put to use on the Hyper-Pack, an over-the-counter factory performance package for the Chrysler Slant Six. Note how the long, curving intake runners nearly fill the engine room.

While the Chrysler Ram Induction system in its original production form disappeared in 1964, the principle itself lives on—in fact, it’s ubiquitous. The contemporary term is pressure wave tuning, and the global automakers have a host of powerful analytical tools for optimizing the property, including Ricardo’s WAVE software. (Additional gates  and passages can also be incorporated to tune for two or more points on the rpm scale.)  On the original Mopar setup, the intake runners were sprawled across the engine compartment, but current manifolds are more efficiently packaged with the runners curled into a bundle, as with this lightweight composite manifold for the current Mustang GT350, below. Ram tuning, as they used to call it, is here to stay.