1978 Pontiac Grand Prix IV (LJ) Dimensions, Size & Specs

With a width of about 1,953 mm (76.9 inches), the 1978 Pontiac Grand Prix IV (LJ) sits on the wider side among sedans from the late 1970s. Many competing full-sized sedans from American manufacturers had widths ranging from approximately 1,900 mm to 2,000 mm (74.8 to 78.7 inches). This relatively broad width contributes to greater shoulder room inside and improves handling stability. Compared to mid-sized sedans of the time, the Grand Prix’s width is notably larger, emphasizing its full-size classification. This makes it more comfortable for passengers but can factor into parking and maneuvering in tighter city spaces.

The curb weight for the 1978 Pontiac Grand Prix IV (LJ) typically ranges from approximately 1,700 kg to 1,900 kg (3,750 to 4,190 lbs), depending on trim and options. This weight is usual for full-size sedans of the late 1970s with large V8 engines and robust body frames. The substantial mass contributes to a stable and smooth ride but also impacts acceleration, fuel efficiency, and braking distances. The suspension and powertrain were tuned accordingly to balance comfort and performance, although the weight does mean the car is less nimble than smaller, lighter vehicles. Overall, the weight aligns with consumer expectations at the time for a luxurious and comfortable cruiser.

Standard residential garages generally measure about 2,400 mm to 2,700 mm (8 to 9 feet) in width and at least 5,000 mm (16.4 feet) in length. Given the Grand Prix IV's length of about 5,597 mm (220.5 inches or roughly 18.4 feet) and width of 1,953 mm (76.9 inches or 6.4 feet), the vehicle would fit into a standard garage but with limited extra clearance. Maneuvering might be tight, especially on the sides, so careful parking would be necessary. The relatively low height of 1,322 mm (52 inches or about 4.3 feet) is well within any garage height limits. Overall, with average garage dimensions, the 1978 Grand Prix IV fits but leaves minimal extra room for storage or opening doors wide inside the garage.

The 1978 Pontiac Grand Prix IV (LJ) represents a continuation and slight evolution from the Grand Prix III generation. Dimensions-wise, the fourth generation retains much of the previous generation’s size characteristics, maintaining a full-size sedan footprint. Length remained fairly consistent, hovering around 5,500 to 5,600 mm (216.5 to 220.5 inches), reflecting minimal downsizing compared to the Grand Prix III. Width and height dimensions also stayed close, ensuring that passenger space and road presence were preserved. The updates were more focused on styling refinement and mechanical improvements rather than radical changes in size. Therefore, owners familiar with the Grand Prix III would notice the IV as a familiar yet subtly updated sized vehicle.

The spacious exterior dimensions of the 1978 Pontiac Grand Prix IV (LJ), particularly its generous width of 1,953 mm (76.9 inches) and length of approximately 5,597 mm (220.5 inches), translate into a roomy and comfortable interior. Front and rear seating areas offer ample legroom and shoulder room, making long journeys enjoyable for all passengers. The wide cabin allows comfortable seating for three in the rear bench with minimal compromise in elbow space. The expansive interior complements the luxury-oriented design, featuring comfortable seats, a broad dashboard, and significant headroom despite the relatively low roofline (1,322 mm or 52 inches). Overall, the interior comfort matches the expectations set by the vehicle's sizable exterior footprint.

Compared to its contemporaries such as the Chevrolet Caprice and Ford LTD, the 1978 Pontiac Grand Prix IV (LJ) sits comfortably within the full-size sedan category with similar dimensional profiles. The Grand Prix IV’s length of about 5,597 mm (220.5 inches) and width of 1,953 mm (76.9 inches) are comparable to the Caprice, which was typically around 5,410 to 5,500 mm (213 to 216 inches) long and similarly wide. The Ford LTD was also in this ballpark, with lengths around 5,400 to 5,600 mm and similar widths. Feature-wise, the Grand Prix IV emphasized personal luxury with upscale trim and options, sometimes offering more premium touches relative to the Caprice and LTD. Dimensionally, all three target spaciousness and comfort, with nuanced styling and equipment differentiating their appeal.

The 1978 Pontiac Grand Prix IV (LJ) was powered primarily by V8 engines designed to deliver smooth power suitable for a luxury-oriented full-size sedan. Common engines included Pontiac’s 400 cubic inch (6.6 L) V8 and the larger 403 cubic inch (6.6 L) V8 options, offering horsepower figures roughly between 170 and 185 hp, reflecting late 1970s emissions constraints. These engines were paired with automatic transmissions optimized for comfortable cruising rather than sporty dynamics. Performance was adequate for highway driving with an emphasis on straight-line smoothness and refinement rather than agility. Suspension tuning favored ride comfort, cushioning occupants from road imperfections. Overall, the Grand Prix IV balanced power with the era’s regulatory and consumer expectations.

The 1978 Pontiac Grand Prix IV (LJ), with its sizeable length (5,597 mm or 18.4 feet) and width (1,953 mm or 6.4 feet), presents certain challenges in tight urban settings but remains practical for suburban commuting. Maneuvering in dense city traffic and parking may require extra attention due to its substantial footprint, especially in narrow spaces and crowded parking lots. However, the car's smooth ride and roomy interior are beneficial for suburban use where longer trips and comfort are priorities. Visibility is generally good, aiding in navigation despite size. Drivers accustomed to full-size sedans of the era should feel comfortable, although modern compact cars would naturally outperform it in tight quarters.

The 1978 Pontiac Grand Prix IV (LJ) is emblematic of the late 1970s American full-size personal luxury car trends, emphasizing both size and comfort despite emerging fuel economy concerns. Its dimensions remained substantial, with length exceeding 5,500 mm (over 18 feet), reflecting a market preference for spacious, prestigious sedans. Styling featured smoother, more aerodynamic lines compared to earlier boxier designs, signaling a shift toward fuel consciousness while maintaining luxury elements. Though not radically downsized, the Grand Prix IV did integrate lighter materials and drivetrain tweaks responding to stricter emissions and safety regulations. The vehicle thus balances traditional American luxury sedan ideals with the changing regulatory and market environment of the late 1970s.