The Legendary Pontiac Ram Air 400 Cubic Inch Engines

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

When I see a Pontiac muscle car my first question is what's under the hood. My excitement builds as I approach the automobile. I feel like a kid on Christmas morning. Will I see the most common engine, which is the small displacement 326 CID? Maybe it's my lucky day and I'll find a Tri-power 389 Trophy motor hiding in the engine bay.

As the hood swings open, the sunlight reflects off the chrome valve covers and air cleaner directly into my eyes.

After the temporary blindness begins to clear, I see yet a third possibility. It's the legendary Pontiac 400 cubic inch 6.6L muscle car motivator and I'm not disappointed.

Join me as we uncover detailed information about this legendary engine and the different Ram Air versions. Discover the big block engine and transmission combination coveted by collectors. We'll also show you a quick way to tell the difference between the 6.6L 403 Oldsmobile power plants and the 400 Pontiac both found in the second generation Trans Am.

When Did They Build the 400

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

What Makes the 400 Pontiac Special

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

The 400 pushed this number up to 360 HP with the same Quadrajet single four barrel. For me, I think what sets this engine apart in the history books is the factory installed high performance Ram Air systems. When someone is talking about a Pontiac Ram Air (numbers II through IV) they’re talking about a limited edition 400 cubic inch muscle car engine 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 breath. Although this included the hood scoop and fresh air intake, it was more about the camshaft, cylinder heads and exhaust manifolds.

These parts boosted power through improved intake efficiency and 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, they increased the lift and duration of the camshaft. They also strengthen the bottom end by using a four bolt main instead of the previous year’s two bolt set up.

The RA 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.

Final Thoughts about the Pontiac 400

This engine found its way into a lot of cars. You can find them in an entry-level Pontiac LeMans or 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 represent a good 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. The 403 has a large oil fill tube in front of the intake manifold leading down to the timing case cover.