1963 Pontiac Grand Prix - The Mysterious SD Grand Prix

Bruce Mihalak of North Ridgeville, Ohio, thought he knew exactly what he was getting into when he answered an ad titled "Super Duty Clone" in the local Car Trader. He was hoping to purchase, arguably, the ultimate '63 GP.

Due to the fortunate foresight and mechanical mastery of a previous owner, the stock, 303-horse, 389 engine; the Roto-Hydramatic transmission; and the highway-geared rear were removed from this Pontiac and in their places were mounted a two-four-barrel, SD-parts-equipped, 421 engine; a four-speed trans; and a 3.42 Safe-T-Track rear. If that weren't enough, the GP also was fitted with A/C, tinted glass, power steering, power brakes, power windows, a tilt column, a vacuum-assist trunk release, a real-out trunk light, 8-Lug wheels, lamp group, and an AM/FM radio with reverb. The cruise-control under-hood unit came in a box for later installation. It seemed to be a perfect blending of early '60s luxury liner and brutal Super Duty screamer.

What Bruce learned by speaking to the seller however, was surprising to say the least. The seller claimed that the man from whom he purchased the GP actually performed the drivetrain swap and said the SD components came out of a rusty '63 Grand Prix. Could it be that a 1-of-3 factory-built SD 421 GP was parted to outfit this Pontiac? Of course, this hearsay would require further verification.

Questions notwithstanding, "I left the house immediately with Pontiac data books in hand," Bruce says. "I saw the GP and loved it, but I really loved it when I started verifying the casting numbers and stampings. It was a no-brainer!" Recognizing a deal when he saw it, Bruce spent $22,000 in August 2004 on a special Pontiac that brought with it the allure of a few mysteries for this police officer to investigate.

First, the VIN stamped on the engine block features a "W" for the plant code. Noted researcher Pete McCarthy told Bruce that all the SDs he has seen were built at the Pontiac plant ("P" code). "W" is for Wilmington, Delaware.

Then there's another twist. In contacting Jim Mattison at Pontiac Historic Services while researching this story, HPP learned block VIN 963W14022 checks out as a '63 GP with a 421 H.O. Tri-Power and a four-speed trans. So, it appears this engine began its life as a 421 H.O. and graduated to SD status by having the parts added later. The engine block casting number 544988 verifies a 421 block.

After viewing a photo of the block stampings, Mattison said, "I've never seen a block stamped with random stamps like this one is. It is my suspicion that someone has restamped this block. I also noticed that some numbers are stamped into the rough casting area [on the head], above the machined surface on the block. The factory never stamped this area." There is also evidence of prior stamping under the VIN, yet the VIN on the block and the motor unit number on the block both appear, as they should, on the paperwork Mattison pulled for verification.

Just exactly what was or wasn't done to this engine at the factory or by others afterward shall remain a mystery, but it doesn't diminish the fact that there are some special pieces bolted onto this block. Rebuilding of the engine at Gellner Engineering in Parma, Ohio, was commissioned by the previous owner who did the swap.