1969 To 1972 Pontiac Grand Prix - A Grand History

Those wanting to create the ultimate high-performance Grand Prix could opt for the L79 428 H.O. Boasting a 10.75:1 compression ratio, the 428 H.O. was rated at 390 hp and featured high-flow exhaust manifolds, a 273/289- or 288/302-degree camshaft, depending upon transmission type, and revised distributor and carburetor settings. Available on the J for $177 or on the SJ for $119, the H.O. engine could be had with either an automatic or manual transmission-but air conditioning was not available with the manual. When combined with axle ratios as deep as 3.90:1, vintage performance tests indicate that a 428 H.O.-powered Grand Prix was a solid, low-14-second quarter-mile performer.

The '69 Grand Prix was a major success, generating large amounts of showroom traffic and magazine exposure. Model-year production totaled 112,486 units-an increase in excess of 80,000 units from the previous year, which included 101,403 Model J and 11,083 Model SJ models. It appears that a total of 1,105 428 H.O. engines were installed-986 of which were backed by the Turbo 400. And 1,014 Grand Prixs received a manual transmission.

1970
Given the success of the '69 Grand Prix, Pontiac would have been foolish to change much for 1970. With that in mind, exterior updates were limited to smaller details such as grille and taillight textures, and the repositioning of exterior trim. The interior was essentially carried over, but a bench seat was now available as a credit option, and only with the Turbo 400.

The 350hp 400 four-barrel was again the standard engine in the Model J, while the low-compression 400 two-barrel remained a no-cost option. The 428 engine from 1969 grew even larger for 1970. An increase in crankshaft stroke from 4.00-inches to 4.21 caused displacement to jump nearly 30 ci to 455. Although referred to in sales literature as "455 H.O.," the new 455 was similar to the 428 H.O. it replaced, but lacked the high-flow exhaust manifolds, and was subsequently rated at 370 hp. Transmission usage remained the same for each application.

An economic recession during this time had many new-car buyers searching for less-expensive models. And since most Pontiac offerings were slightly higher priced, Pontiac had fallen as far back as sixth in sales during the '70 model year. Grand Prix production not only reflected this, but it was also impacted by the competitive models being offered by other manufacturers. Total production fell to nearly half that in 1969 with just 65,750 units produced. The Model J represented 60,165 of that total while the remaining 5,585 units were SJs. Pontiac's 455 four-barrel engine was installed in 2,665 Grand Prix Model Js at a cost of $58. And manual transmission-equipped Grand Prixs totaled just 500 units.

1971
The Grand Prix received some significant design changes for 1971. The most notable included single headlights that replaced the previous dual-style treatment, a new decklid with pronounced boat-tail styling, and new bumpers front and rear. Interior changes were limited, but the same overall theme was retained. It seemed as if excitement about the Grand Prix was peaking. Enthusiasm regarding what was underhood was another story, however.

General Motors imposed a compression-ratio restriction on all divisions for 1971. By limiting the ratio to a maximum of 8.5:1, engines could operate on lower-octane unleaded fuels, ultimately reducing tailpipe emissions. However, the reduction negatively affected engine output. If that weren't enough, a new method of net rating output-which more closely represented actual engine output when installed in a vehicle with all accessories connected and operating in normal underhood conditions-made it seem as if the '71 engines were mere shadows of their former selves.

The 400 four-barrel remained the standard powerplant in the Grand Prix Model J, but its new 8.2:1 compression ratio caused its gross horsepower rating to slip to 300. Its net rating was 255 hp-or what appeared to be nearly 100 less than the 1970 offering. As in previous years, the three-speed manual transmission was standard, while the four-speed manual and Turbo 400 remained extra cost options. Rated at 325 gross and 260 net horsepower, the 455 four-barrel was no longer available with a manual transmission. And the 400 two-barrel was cancelled.

For 1971, the SJ package retailed for $195 and again included such items as the 455 four-barrel engine, Rally gauges, custom lamp group, and specific SJ identification. There were, however, a few new features in the package such as vinyl accent stripes, body-colored sport mirrors, and the Delco X battery-a high-tech unit that was completely sealed and required no periodic maintenance while offering higher power reserves.

As promising as 1971 looked for the Grand Prix, the UAW launched a massive strike on September 14, 1970, that halted vehicle production at every GM assembly plant across the country-including the three that built Grand Prixs. Sixty-seven days later, the strike was officially resolved, but it took some plants several weeks after that to resume production. The Grand Prix's Lakewood, Georgia, plant, for one, sat idle until January 29, 1971, greatly affecting availability.