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 , 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.
While the four-bolt main bottom end was reportedly treated to typical machining and replacement parts, there are no details on whether or not the forged-steel SD crank or forged SD rods were added. The cam is a custom Crane solid roller with 286/294 degrees duration and 0.525/0.543 lift. (A factory solid lifter No. 10 SD stick features 308/320 degrees duration and 0.445/0.447 lift with 1.65 ratio rockers.) Head modifications are unknown as well for this particular engine, and while roller rockers are an obvious choice given the cam, the ratio eludes us. Though we can't comment on the mods for these heads, factory No. 9771980 units were SD exclusives that outflowed production offerings and were originally fitted with 2.02/1.76 valves-larger than the valves in regular production heads.
A compression ratio of 11:1 is stout for the street, but it's somewhat better than the factory SD ratio of 12:1. Mixing air and fuel is a pair of 500-cfm Carter AFBs, and beneath them is a factory '63 SD aluminum intake No. 97770859. Spark is provided by a Delco points-type distributor and a stock coil, via Packard wires and AC plugs. Factory '61-'62 SD No. 540297 right and No. 540298 left cast-iron exhaust manifolds usher burnt hydrocarbons through a 2.5-inch exhaust system featuring Flowmaster mufflers, when the cutouts are closed.
A '63 Borg Warner T-10 four-speed trans is delivered the engine torque via a stock replacement clutch. And a 3.42 Safe-T-Track unit at the far end of the driveshaft distributes the twist to a pair of smoking 225/75R14 Mastercraft A/S 4 radials.
The factory interior remains, and the suspension and braking system refurbishing were all handled by the previous owner who did the swap, thus leaving Bruce little to do but research the GP's interesting engine and drive those 8-Lug wheels off his Pontiac.
With SD induction, heads, and exhaust on the 421 engine representing the best Pontiac had to offer in the early '60s, mounted in a vehicle that was factory-designed to balance luxury and performance, Bruce's '63 GP seems to have it all. Add in a dozen or more comfort options like this one has and you'll be lucky to ever get a look at this machine standing still. "It's got the ride of a Caddy with the engine of a musclecar," Bruce says. I've done nothing to the Grand Prix but drive it since I bought it." It may not be 1 of 3, but Bruce knew what he was getting into when he bought it-the problem now will be getting him out of it!

Photo Gallery: 1963 Pontiac Grand Prix - High Performance Pontiac Magazine



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