It's difficult to grasp how an engine can generate enthusiastic buzz more than 40 years after its inception, but mention Pontiac's Super-Duty 455 and some Firebird fanatics get wide-eyed while others stand at attention in its presence. Introduced at a time when others were stepping away from performance, the SD-455 forged a mystique that became ingrained in the minds of those who read about it in vintage automobile magazines, as well as anyone who's experienced its awesome acceleration.
HPP has presented much insider information about the SD-455 and its development over the past several years. That includes comments from the Pontiac engineers directly involved with the program of how it was compromised for production. So what about the performance enthusiasts working for the Division who had no role in its development? Were they at all aware of how much potential the SD-455 possessed?
Gregg Peterson knows firsthand. A former Pontiac engineer, he arrived at PMD in 1969 and was immediately drawn toward the SD-455 program. Working closely with those associated with it on other projects, he took a keen interest in the SD-455 and gathered as much developmental information as he could. He then used it to improve the performance of his own '74 Super-Duty Trans Am. We're excited to share with HPP readers for the very first time that info and some of the internal SD-455 documents Gregg obtained.
On October 7, 1971, Pontiac Engineer D.L. “Skip” McCully prepared an internal memo contain
Gregg grew up feeling that Pontiac built America's most exciting passenger cars during the '60s, and with his love of performance automobiles he decided to make designing them a career. When it came to seeking an employer, he immediately sought out Pontiac. "I was drawn toward the Division's hell-raising attitude, the risks management was willing to take to make its cars better and more innovative, and how it was always pushing the technical limits of its talented industrial designers."
Gregg began his work with Pontiac in 1969 as a student engineer while attending the General Motors Institute of Technology (GMI) in Flint, Michigan. The '701⁄2 Trans Am was very near its public release and upon seeing the developmental prototype for the first time, Gregg recalls, "I thought it was drop dead gorgeous. I couldn't believe a car like that was actually going into production. I always felt that a R/A-IV–powered '701⁄2 T/A was, and still is, a very serious machine."
Pontiac engineer Herb Adams headed a Special Projects group that included Skip McCully, Tom Nell, and Jeff Young. The engineering team was responsible for many programs—one of which was the SD-455. "I always talked with them," says Gregg. "They were very talented and passionate about Pontiac performance. They knew I was a performance enthusiast too, so I was asked to join Herb's NASCAR race team. Herb wanted to take Pontiac to the highest levels of performance on the street and race track and was looking to create an engine to achieve it."
In its 310hp configuration, which consisted of an 8.4:1 compression ratio and the 041 cam,
Gregg first learned about the SD-455 while it was in development. "It was around 1970 and one of my student assignments was in the Powertrain group. Skip was working on a low- compression, high-performance 455 to compete with Buick's Stage 1. I believe it was this program that led to the '71 455 H.O. Jeff Young was in the Engineering lab working on a new round-port cylinder head, which turned out to be for a race-bred engine—the SD-455."
Immediately upon learning of the SD-455 project, Gregg knew he had to own one. "Every key component was redesigned to improve performance and durability. As opposed to an improved street engine, the SD-455 was actually a detuned race engine. Management had legitimate concerns about dedicating resources to low-volume engines at a time when Pontiac was facing difficult challenges in so many areas, but there was a very high level of enthusiasm at Engineering because of the SD-455."
Ron Genaw ran Pontiac's dyno lab, and Gregg visited him on a regular basis. "Ron had built some seriously fast street Pontiacs, and in my opinion was an ideal person to be part of the Super-Duty development. In stock trim the SD-455 was capable of producing more than 400 gross hp. I recall a dyno test of a developmental SD-455 that had 12.5:1 compression, a modified Edelbrock intake manifold, a Holley four- barrel carburetor, an aggressive camshaft, and tubular headers. It put out about 600 hp and 600 lb-ft of torque. You could literally hear it running throughout the Engineering complex."
Herb Adams introduced the SD-455 to the world at Pontiac’s long-lead press preview on June
The SD-455 was planned to be an available option in several '73 Pontiac models and a number of pilot cars were built. A long-lead press preview took place at the Milford Proving Grounds on June 28, 1972, and Gregg was selected to work it. "Herb was presenting the SD-455 to the press writers that day," he adds. "He had a few different developmental Super-Duty Trans Ams on hand for performance testing, and I was assigned to run the dragstrip, which was setup on the north end of Black Lake."