A Guide to the Iconic Pontiac Ram Air 400-Cubic-Inch Engine

The Pontiac 400 Cubic Inch Engine
The Pontiac 400 Cubic Inch Engine. Photo by Mark Gittelman

When car collectors encounter a classic Pontiac, the first thing they do is pop the hood, hoping to see the legendary Ram Air 400-cubic-inch engine, which was part of the performance option packages that General Motors offered in the late 1960s. Most of the time, potential buyers will encounter the most common engine, the small displacement 326 CID. If it's their lucky day, they'll maybe find a Tri-power 389 Trophy motor hiding in the engine bay. But if they're really lucky, they'll encounter the 6.6L 400 big block.

Origin of the 400

The Pontiac Motor Division built the 400 from 1967 through 1978. Although it found its way into many 1979 automobiles, those were actually purpose-built leftovers manufactured in 1978. Nevertheless, this is an amazing 12-year run at a time when car makers changed an engine's displacement every few years. In fact, the Chevrolet 454 7.4L is one of the few that GM kept in production longer.

What Makes the 400 Pontiac Special

Pontiac grabbed a 389 block used in the high-performance Catalina, as well as the Lemans and GTO, and punched it out to an even 400 cubic inches. They found that the engine provided massive amounts of low-end torque and rock steady high RPM power output. The 389 posted numbers in the 330 horsepower range with a single spread-bore, four-barrel carburetor.

The 400 pushed this number up to 360 horsepower, with the same Quadrajet single four-barrel. What sets this engine apart in the history books is the factory-installed high-performance Ram Air systems. When someone talks about a Pontiac Ram Air (numbers II through IV), they’re talking about a series of limited-edition, 400-cubic-inch muscle car engines built from 1967 through 1970.

High-Performance Ram Air Versions

Pontiac built the Ram Air versions in a total of five different stages. The original set up in 1967 concentrated on improving how the engine would breathe. To that end, they included a hood scoop and fresh air intake, but tweaks to the camshaft, cylinder heads, and exhaust manifolds were key as well.

These parts boosted power through improved intake efficiency and by reducing exhaust back pressure. The major difference between the original Ram Air in 1967 and the Ram Air II in 1968 is the shape of the cylinder head intake ports. They went from a D-shaped port to a round one. This change pushed advertised horsepower past 365 HP for the first time.

On the Ram Air III version, built in 1969, Pontiac increased the lift and duration of the camshaft. They also strengthened the bottom end by using a four-bolt main instead of the previous year’s two-bolt setup.

The Ram Air V is a completely different story. These were built to power cars for the SCCA Trans Am Racing Series. Pontiac milled the deck on these blocks to boost compression and raise horsepower. It's believed they built less than 500 in total.

Where to Find the 400

This engine found its way into a lot of cars, from an entry-level Pontiac LeMans to a prestigious GTO Judge. You'll also find them in family cars like the Bonneville and Catalina station wagons. With the supply far exceeding the demand, these engines make your potential classic car buy a great value. And parts are still readily available for rebuilding.

In fact, high-performance replacement parts supporting the Ram Air crowd provide an opportunity to boost power output. Keep in mind that factory-paired 400 engines with 4-speed manual transmissions are the most coveted by collectors. Finally, if you're looking at a classic 1979 Pontiac Trans Am muscle car and you think the 6.6L means a 400, you're only partially right.

When Pontiac exhausted their supply of the 400 power plants built in 1978, they filled the remaining need using the Oldsmobile 403. Thankfully, there's an easy way to tell these two apart: The Pontiac version has the oil fill on the valve cover, while the 403 has a large oil fill tube in front of the intake manifold leading down to the timing case cover.