1965 Pontiac Bonneville

Convertible U/K

6.9L 6900CC 421Cu. In. V8 GAS OHV Naturally Aspira

Automatic

26267 5E165575

Gasoline

Buyer's Guide from Hemmings Classic Car April, 2007 - Matthew Litwin If you've been thinking about cruising the local boulevard in a classy convertible, but find yourself longing for the power under the hood that only a muscle car provides, perhaps it's time to take another long look at Pontiac's restyled 1965 Bonneville convertible. Why buy a Bonneville convertible? It has long been associated with having a graceful combination of elegant yet sporty styling, combined with shocking power and "Wide Track" suspension, a combination which led to the entire 1965 Pontiac line being the recipient of Motor Trend's Car of the Year. Perhaps more than ever, the Bonneville convertible is climbing the ladder of desirability in the powerful big car market. There is something for everyone residing under the hood, and mated to the seven engine choices are three different transmission selections. Pontiac engineers reached a new pinnacle in design styling mid-decade. Subtle changes to the new sheetmetal provide a more chiseled stance with a lower hood and accentuated bodylines, without losing an ounce of grace. While their GM brethren shared the basic sheetmetal, buyers--and certainly collectors today--can easily distinguish the Pontiac from the rest of the market simply because of their exceptional front ends. The 1965 Bonneville and the Catalina, Grand Prix and Star Chief are almost identical to the 1966 models, so everything mentioned in this Buyer's Guide applies to those models, as well. The main visual difference between the two years is the headlamp treatment; the 1966 models have a less ornate headlamp bezel. But all else, including the suspension, brakes, powertrain and the rest of the body, is the same. ENGINES Four different 389-cubic-inch engines were available, all with a 4.06 x 3.75-inch bore and stroke, while most everything else varied. The 389 also happened to be the base offering: Bonnevilles equipped with a manual transmission arrived with a 333hp version, with a 10.5:1 compression ratio and a four-barrel carburetor that plants 429-lbs.ft. of torque. Those that arrived with the Turbo Hydra-Matic automatic transmission had a standard 325hp 389, also with a 10.5 compression, four-barrel carburetor and 429-lbs.ft. of torque. An economy 389 was available at no cost, but with a two-barrel carburetor and an 8.6:1 compression ratio, it pushed out only 256hp. This can be found with a Turbo Hydra-Matic. Called the poor man's Tri-Power, a change of induction on the 389 allowed three two-barrel carburetors--when combined with a 10.75:1 compression ratio--to produce 338hp and 433-lbs.ft. of torque; The 389 Tri-Power was a $133 option. A mere $5 more could fetch a buyer one of the three 421-cu.in. engine options, in this case, a 338hp version that features the same 10.5 compression, a four-barrel carburetor, and 459-lbs.ft. of torque. Again, a change of induction meant the highly sought Tri-Power arrangements could be obtained. With a compression ratio of 10.75:1, the $272 option produced 356hp, while the 421 High Output V-8 option for $376 cranked out 376hp. Common to all Pontiac V-8s, each engine version has its own specification cylinder head that was used to maximize that engine's horsepower and torque potential. See the adjoining sidebar on page 89 for a complete listing of cylinder head numbers. Use these cylinder head numbers to check to see if the Bonneville you're buying is fitted with the correct engine. According to well-known Pontiac engine builder Jim Taylor, "They are all terrific engines; however, they do have one issue. Starting around the 45,000-mile mark, the nylon teeth on the aluminum cam gear would start to shear off. The oil pressure light would flicker when at an idle, so the first thing we'd do is pull the fuel pump off as it's located right next to the timing chain. If bits of nylon teeth were in there, then there's a good chance that they were getting stuck in the oil pump pickup. We used cast-iron gears from Melling to rectify the problem, as well as a heavy-duty timing chain from the old Pontiac four-cylinder engine." TRANSMISSIONS The Bonneville was available with both a manual or Turbo Hydra-Matic automatic transmission. Two different manual transmissions were available: a three-speed and a four-speed. The three-speed arrived as standard equipment mounted to the available engines, except the 325hp 389. The shift lever can be found on the steering column--its standard position. However, it could be ordered as a console shift--for models ordered with bucket seats--or as a floor shift unit. This last variation utilized a Hurst linkage. The four-speed--a $231 option--could be obtained in the same manner, except that it was not available with a column-mounted shift lever, and floor-mounted shifters also utilized a Hurst linkage. The new-for-Pontiac Turbo Hydra-Matic automatic--also a $231 option, except when coupled with the 325hp, 389-cu.in. V-8--could only be obtained in two variations, if you will, meaning that the gear selector is column- or console-mounted only. The new transmission was touted as "stronger, smoother and more responsive in almost every way." In fact, it seems the only complaints from early buyers were from those who were unhappy with the shift points--they were too smooth. "They are virtually bulletproof transmissions," according to Jim Taylor. "They can withstand a lot of abuse." Even if a problem arose, these units can be rebuilt, as all the parts needed to do a quality rebuild are readily available and cheap. DIFFERENTIAL A Hypoid unit with semi-floating rear axles arrives as standard equipment. However, a vast quantity of gear ratios can be found in the differential, depending upon engine and transmission choices--at least factory stock--according to the November 1964 issue of Motor Trend. For instance, if the Bonneville arrived with the Turbo Hydra-Matic, anything from a 2.41:1 to 3.23:1 gear ratio was installed, whereas the three-speed manual commanded a 3.42 gear when the 376hp, 421-cu.in. V-8 is under the hood; a 3.23:1 ratio was utilized throughout the rest of the three-speed/engine lineup. The four-speed commanded only a 3.42:1 gear ratio. Mind you, these were just the standard gears, as further ratios were available as optional equipment, depending upon engine selection. SUSPENSION Though an independent front suspension--complete with A-arms, coil springs and tubular shocks--and a four-link system that includes tubular shocks and coil springs in the rear, grace the Bonneville, it was a redesigned system. In short, it provides better stability with lower unsprung weight than the previous models. As with most cars, the spring rates are governed by the size and weight of the body they support. Unless the Bonneville you're interested in buying has been sitting on the ground for 30 years, or was driven on salty roads regularly, the suspension should be holding its own with the usual wear. New bushings, bearings, shocks and springs, including heavy-duty versions, are available. BRAKES Nothing to get too excited about here, other than the 10 percent increase in front brake linings over the previous model year. The cast-iron drums feature larger fins to assist with the cooling. Measuring 11 inches in diameter front and rear, the only difference arrives in the form of depth: the front drums are a full 3/4 of an inch deeper than the 2-inch rears. This equates to a lining area of 188.5 inches to stop the nearly 4,000-pound convertible, only enhanced by the $43 optional power-assist system. Still, a Motor Trend road test published in February 1965 suggested that potential buyers spend the extra $121 for the much-sought-after-today eight-lug aluminum wheels/hubs, because of their ability to cool more quickly than their steel counterparts. While the standard cast system--including wheel and master cylinders--can all be acquired or rebuilt, those seeking suitable replacement eight-lug hubs were in for a long haul (until recently, when Arrowhead Components began to reproduce them; at the time of this writing, they should be available through multiple parts suppliers shortly, if not already). The chrome trim rings, center caps and the special lug nuts can be bought separately from Ames Performance Engineering. BODY/FRAME Supporting the long, 221.7-inch body is a perimeter frame sporting a 124-inch wheelbase; this is the same frame used on the Star Chief--the Catalina and Grand Prix models had a shorter frame to suit their shorter, 121-inch wheelbase. Several improvements resulted for the 1965 model year, such as a reduced weight, and improved strength that transferred directly to the body. Due to lower side rails, the floor was improved to make ingress and egress easier. As mentioned, the body is somewhat larger than the previous model, accentuating the flowing design with the tasteful application of chrome affixed to the lower body panels. The sporty design also blended barrel-shaped, stacked headlamps--with a visor overhead compliments of a slight protrusion from the front fender--not to mention a split grille and turn signals integrated into the lower front bumper. The convertible also features a rear window originally made of 1/8-inch tempered glass. According to a 1965 statement from chief engineer John DeLorean, "This gives the best combination of visibility and durability." For increased ventilation, owners can unzip and lower the window, and it doesn't have to be removed to lower the top. The tops themselves were also slightly redesigned to present the convertible as having more of a hardtop look. The ever-threatening tin worm is no stranger to the big Pontiac. However, reproduction rocker panels and floor pans are available, as are new door skins and patch panels, trunk floor pans and B-pillar patch panels. A little hunting might net you a rust-free fender; however, these are starting to become scarce. INTERIOR There's plenty of room in the Bonneville's interior, no matter how wide or tall you may be. The standard bench seat is quite welcoming, and was available in either long-lasting Morrokide vinyl or optional leather. A power bench seat, buckets, and power left bucket seats, as well as a center console, are all options that can be found in the Bonneville. The dashboard is deliciously dressed with a real walnut, adhesive-backed insert, along with a standard array of gauges and a clock. Pontiac's new automatic temperature-control air conditioning could have been obtained for a then-lofty $430--it's a set-it-and-forget-it system that maintains a predetermined temperature. The main difference between the '65 and '66 models is the three center gauges. For 1965 they are round; then Pontiac changed them to a rectangular shape for 1966. Also for '66, there is no wood trim on passenger side of the dash. Though the prestigious Pontiac is quite lengthy, steering it is simpler with the addition of power steering, effectively leaving the lock-to-lock turns at the wheel at 4.2. And if you need to sneak cousin Jimmy into the drive-in, he'll be quite comfortable in the car's 23.4 cubic feet of usable luggage space. Convertible models have long been associated with the issue of a good seal. Keeping the weather out will get difficult as the weatherstripping ages, but just about every piece of weatherstripping needed, including the windshield seal, is being reproduced. New convertible tops, molded carpet sets, door panels and upholstery kits in the original material are available in a variety of colors.