From the onset, Imran had envisioned this GTO as the spiritual successor to the prototype that was featured in Hi-Performance Cars magazine and elsewhere. That meant that the engine would be built to the original 455 Super-Duty specs, not to the production version. This allowed him to include stuff that had been eliminated due to the emission certification.
The intake manifold is one area where the prototype was outfitted differently than a production version would have been. The Hi-Performance Cars magazine test car was outfitted with the No. 485640 aluminum intake manifold.
A handful of these intakes were cast but rejected for production due to their lack of heat retention, which negatively affected emissions. It was replaced with a cast-iron version for the production Formulas and Trans Ams, and the castings on hand were put into the parts network. Imran was fortunate enough to actually find one of these rare intakes and included it in the engine build.
Secondly, the engine could make use of the Ram Air IV's 308/320-degree camshaft profile and 1.65:1 rockers, which would make a huge difference in overall performance. PMD Special Projects engineers knew the secret of the 455 SD's performance was the camshaft. Many of them were frustrated and disappointed that the "big" cam couldn't be used in production. Imran's engine would employ this critical element and benefit from the additional duration and 0.520-inch lift. The actual cam featured the correct cam gear and was from Melling, an OE supplier to Pontiac.
The engine was machined and balanced by Gerry Bartel at The Balancing Act and was assembled by Imran. Its block was bored 0.030 over and fitted with Keith Black 9.5:1 forged pistons with Total Seal moly rings. Federal Mogul bearings were used for the mains and rods. The rest of the engine was stock, including the correct 455 SD high-volume oil pump. Per the Pontiac Service Bulletins of the time, the galley plug near the distributor had a 0.030 inch drilled in it to lubricate the distributor gear. This modification also dropped the oil pressure from 80 to a more reasonable 60 psi.
Imran went the extra mile for authenticity, managing to find correctly date-coded NOS spark plug wires and AC spark plugs in their original boxes. He even managed to find a correctly date-coded AC oil filter. The engine was painted as it would have been with an early '73 release-the light blue that was used starting in 1971. Engines built after March 15, 1973, used a darker blue, indicating the revised emission control system. Talk about sweating the details!
As expected, the finished engine was quite a bit healthier than the production SD-455. With just the cam change, 1.65 rockers, and aluminum intake manifold (which may or may not have a noticeable effect on power), the big SD responded on the SuperFlow dyno with 415.3 hp at 4,800 rpm and a whopping 514.7 lb-ft of torque at 3,500 rpm. The potential of the Super-Duty, even with the low compression, is very impressive.
Additionally, the pre-production prototype was equipped with a four-speed manual transmission, and this GTO was built as an automatic. A conversion to four-speed certainly wasn't out of Imran's capability, but getting the necessary parts was a huge task. The majority of the componentry came from a locally sourced '73 four-door Grand Am, one of the 187 four-speed cars built and perhaps 1 of 20 four-doors. Unfortunately for that particular car, it was rusted far beyond salvaging, but it did provide the pedals, linkages, shifter, and console. Imran went with a Borg-Warner Super T-10 out of a late '70s Trans Am rather than the Muncie M20 specified for production.
Out back, the original rearend was rebuilt and fitted with 3.42 gears and a Safe-T-Track. The correct steel wheels and baby-moon hubcaps are set off with a set of reproduction G60-15 Goodyear Polyglas GT tires.
Since its completion in the spring of 2008, the GTO that never was has taken a Best in Class at the 2008 Sports Car & Vintage Auto Festival in Farmington, New York; the Most Outstand-ing Musclecar at the 2008 Performance World Custom Car Show in Toronto; and a GTOAA Concours Gold-Modified at the 2008 GTOAA Convention in Saratoga Springs, New York. This is the car that really could have enthusiasts taking a new look at '73 GTOs, and '73-'77 Pontiac A-bodies in general.
What is next for Imran and his one-of-zero-built 455 Super-Duty '73 GTO? "Now that I have the show awards, I really want to drive this one a bit," he replied. "It has a very powerful engine, yet it's also very docile. It idles at 600 rpm, and you can set a glass of water on the air cleaner and it won't move."
Imran Chaudary is a doer like no one I've ever met. Even if Pontiac couldn't do it, Imran could-and did!
Imran also credits Andy Pooni, Mueen Abdullah, and Kamran Chaudary for all their help in the build. "Most of all, I want to say thanks for the patience of my wife, Asma, and the kids. I could not have done it without them," Imran said. "I also want to thank the members of the Classic GTO Club of Ontario and the guys on the A-Body Site for their assistance with research."