16-17 January 2014
1958 Pontiac Bonneville 'Tri-Power' Convertible
- Chassis no. P558H1045
Sold for $99,000
- AACA Senior National First Prize winner
- Desirable 300-horsepower Tri-Power engine
- An outstanding highway cruiser
You don’t have to know anything about a ’58 Bonneville Convertible to appreciate it. It is a car that could only have come from America; it was 211 inches and 4,040 pounds of steel and chrome, and it had all of the hot engine options you could ever want. In its first year of having its own line of cars, Bonneville was among the hottest cars in the red-hot GM lineup, and a Tri-Power Bonneville Convertible paced the 1958 Indianapolis 500. It was an expensive and exclusive car, though—both price and production were comparable to Corvette—and only 3,096 convertibles sold that first year.
Beyond the styling, Pontiac was a high-performance engine company with its own unique offerings. The 370-cubic inch V-8 was overbuilt, dependable, and supremely powerful, especially with the Tri-Power/Hydra-Matic transmission combination, which yielded 300 horsepower, thanks to 10.5:1 compression and a high-lift cam. Hot Rod tested a Tri-Power sedan in 1958, and they found that it was capable of 60 mph in 7.6 seconds, but the convertible does weighs about 200 pounds more than the sedan, so it would be a second or two slower. (As few enthusiasts today are buying Bonnevilles to win drag races, it’s an easy trade-off to make for convertible style.) A Rochester fuel-injection setup that was rated at 310 horsepower was also available, but in testing, Motor Trend found that the Tri-Power was actually faster and, of course, much less trouble.
Restorations of 1958 Bonneville Convertibles are difficult and expensive, as supplies of NOS parts and parts cars are both highly limited. Fortunately, this car has not only had an amazingly well-preserved restoration, but the consignor has also ensured that it is in top running condition. The carburetors are freshly tuned, and a new top and wide whitewall radial tires complement the interior work, which includes new color-keyed belts. A recent all-day rally has demonstrated the car’s ability to run at freeway speeds without difficulty. In fact, this car would not be available if the consignor did not think it was too nice to be exposed to the salt air of his beachfront home.
Any fan of the Bonneville Convertible knows that Tri-Power ’58s seldom trade hands. Finding one ready to drive or show, with all needs attended to, is an annual event at best.
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