1969-'70 Pontiac Grand Prix SJ

1969-'70 Pontiac Grand Prix SJ
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Buyer's Guide from Hemmings Muscle Machines

August, 2009 - David Traver Adolphus

The new 1969 Grand Prix was big no matter how you measured. Big new 118-inch wheelbase, big new SJ model with 370 base horsepower from the big 428. It was a big showroom success, too, with Grand Prix sales up an astonishing 225 percent over '68. Even the SJ model pushed big numbers; over 10,000 sold. Then it got even bigger, when, in 1970, Pontiac rectified the engine lineup and brought out the new 455.

Good thing, too, because the '68 "was a disaster," said stylist Bill Collins in Pontiac 1946-1978. "Nobody bought it. It looked like a big fat turkey, and I would give John [Z. De Lorean] the credit for the idea of taking the A-body, which was less expensive, and building a new car on it."

Actually, John Z. was working a little with smoke and mirrors when he signed off on the design: No, that's not an A-body you see there--see that extra half foot of hood? Presto! It's a G-body! It even fools you from the drivers' seat: There is enough sheetmetal out there to make you think you might be in a Cadillac--no coincidence--but behind the driver, it's not that big, only five inches longer overall than a Tempest.

In fact, it was the Tempest that made it possible. Work on the '69 GP began in early 1967, using the Riviera look as a starting point and the B-body as the platform. But the new A-body perimeter frame presented some interesting opportunities. Wrapping the sheetmetal down around the edges helped strengthen the whole body structure, while isolating it on rubber mountings. The Wide Track body was nothing but good for styling, both wider and lower.

De Lorean was already cracking the whip to get the new '69 done on time, when in mid-April a memo from Pontiac Engineering's Ben Harrison crossed his desk, suggesting a unique platform for the car. Within four days, he'd signed off on a clay model.

Styling was a curious mix of muscle and classicism. The nose was a clear reference to both pre-war Pontiacs and the classics of the era, while the ultra-long hood just said "muscle." The rear end, however, showed a distinct Le Mans family resemblance.

The GP did about half as well for 1970 as '69, even with the 455--credit cousins Monte and Cutlass for that. They had more than a passing resemblance, but both outsold the Pontiac while sharing zero sheetmetal, which is the fundamental issue in shopping for any Grand Prix, SJ or not. There is universal agreement that even an experienced restorer should think twice about buying a project car: Parts are just so hard to find that you'll never get the thing done. Not figuratively "never," but literally.

Checking the "UPC Y97" option in 1969 got you the complete code 324 SJ package with the 370hp 428, but shelling out another $119 for option L79 added the 390hp H.O. version. Also available as a GP J option, it added the 20hp via 10.75:1 compression, versus 10.5; revised exhaust manifolds; aggressive cam; recalibrated ignition timing and carburetor settings. You could get it with either the four-speed or Turbo Hydra-Matic 400, but the H.O. didn't come in a four-speed with A/C. The 370hp engine only came in the Grand Prix, although a 360hp version was standard in Bonnevilles and optional on Catalinas, Executives and Venturas, as was the H.O.

The only major change between '69 and '70 cars was in the engine: The 428 was retired for good, and the new 455 introduced. Coming in only one delicious flavor, the 370hp 10.25:1 compression mill was more of what Pontiac was known for: power. And that power was made lower down than the 428: 500-lbs.ft. at 2,700 RPM.

Interchangeability between Pontiac engines is vast and common, so retrofitting a 455 into a '69 is not unusual. The six years of 455 production leaves more used parts around than the three years that 428s were built. We've seen some Pontiac materials that said you could get the WG-code 360hp 455 (10.0:1 compression) with a manual transmission, but haven't found proof that any were built that way. Complete, date-coded 455s and 428s are both scarce.

The Pontiac 428 and 455 used in 1969 and 1970, respectively, both have their displacements cast into the outside of the block, one on each side, near the engine mount lugs. But to know exactly what you've got, you should find the stamping on the right front side: In 1969, WF for a 370hp/manual transmission, XF for 370/AT, WL for 390/MT and XG for 390/AT; in '70, WG for manual and XF for automatic.

In cars coming from hot, dry places, check for water in place of coolant, which will have eaten up the timing covers, freeze plugs, radiator core and heater core.

Like many other Pontiac engines, the 428 and 455 are prone to leaks from the rear of the oil pan gasket. Ron Panzer of the Grand Prix chapter of Pontiac-Oakland Club International (POCI) says this is often mistaken for a rear main seal leak, but that rear mains are often not at fault, so don't be scared by a slick back there. He recommends neoprene gaskets, RTV sealant, Oil-Dri and a drip pan.

"Most '69 GPs had a cracked fan shroud from all us mechanics leaning on it trying to service the engine," advised Ron. "The engine is so far back from the grille, you had to climb on the bumper and lay on that shroud. It is a royal pain to service that engine... fan belts, water pump and hoses are all tough to reach."

Choices were the overwhelmingly popular M40 Turbo Hydra-Matic 400, or M21 Muncie four-speed. Literally 99 out of 100 Grand Prixs had the automatic, and while a higher percentage of four-speeds went into SJs, it's still thought that only 672 cars or so were made that way. They're definitely worth a premium, so get it authenticated before laying down the dough.

GM claimed lifetime service from its transmission fluid, but time has shown that changing it every other year makes a TH400 happy. In TH400s, pull the dipstick and give the transmission fluid a sniff--burned is bad.

In a four-speed, even less maintenance is required. You might want to keep an eye on leaks from the side cover gasket, which aren't serious, but can get messy. "Parts are starting to get a little difficult to find," says Ron, so nab cluster gears or a 27-spline mainshaft while you still can. As with other options, it's possible that an M20 wide-ratio or even three-speed could have found its way into a Grand Prix SJ, either from the factory or dealership, although it was never officially on the option sheet.

The most common differential is the GM 3.23:1, the standard offering for a TH400 with A/C or 370hp four-speed with A/C. There was also a 2.93 (economy), 3.08, 3.36 (standard in non-A/C H.O. TH400), 3.55 (performance; standard in some four-speed configurations) and 3.90. GM literature from '69 says that most ratios weren't available with A/C. From the cars we've seen, the inexpensive Safe-T-Track limited slip was common. All of these durable axles were used throughout the Pontiac lineup, and are easily sourced.

Not on the H.O. SJ option sheet were Pontiac's 3.73, 4.11 or 4.33 rear axles. But as the 3.73 and 4.11 were offered on the H.O. in the full-sized cars, they certainly work in the GP and we wouldn't be surprised if a set snuck in there.

For a long wheelbase car with a big door opening (check out the hinges, which need lubrication and often wear out), the GP is very stiff, with many of the characteristics of a unit-body car in body-on-frame construction.

Suspension is conventional, independent front with upper and lower A-arms, coil springs and an anti-roll bar; rear control arms and coil springs. Heavy-duty suspension is also common on SJs. With any car, watch for the hood bouncing on your test drive, a sign of a wobbly front suspension (or worn-out hood hinges, another common issue). It's a nose-heavy car, so eyeball front-to-rear attitude for signs the front suspension is sagging, and bear that weight in mind while cornering. All the suspension components are available over the counter.

1969 marked the first year for GM's single-piston front calipers, and it only stopped using them about a week ago. Expect some nosedive as all that weight transfers to the front under braking, and do not lock 'em up in a fast curve. Pontiac power brakes, a very common if not universal option on the GP, should have a nice high, firm pedal and engage smoothly within the first couple of inches of travel. Grand Prix brakes are a mixture of common Pontiac parts and unique Grand Prix items, but the GP parts are available.

Fourteen-inch stamped steel wheels with wheelcovers and white-line 14-inch belted bias tires were standard on the SJ, but we've probably seen more of them with optional Rally II wheels than the base. This is a lot of car for 14-inch wheels, and a lot of car for bias tires. Considering what it's capable of, you'll be a lot happier on a set of radials, especially in braking.

But if you're a stickler, high-quality reproduction 14-inch Rally II wheels are available, with 15s in seven, eight and 10-inch widths. The 14 x 6, 14 x 7 and 15 x 7s

will all fit with no issues, the 15 x 8 and 15 x 10 will require adjustments. Correct lug nuts, trim rings and center caps are all plentiful, as are things like wheel studs and correct finishes for restored wheels.

You're almost better off finding a craftsman with an English wheel to build you new sheetmetal or a patch panel than trying to find a used piece. Specialist disassemblers such as Frank's Pontiac Parts are your best source for used body panels, but don't expect a NOS fender. It's also worth checking in with the western specialty salvage dealers, like Desert Valley Auto Parts in Phoenix, Arizona.

Joining the Grand Prix chapter of POCI may help you hook up with someone with a hoard, but a parts car is a good investment for a restoration. They do exist, as there was a period during which people bought cars for their engines and junked the bodies. The swap meet at the annual POCI convention is usually the place to find rare GP parts. Good floor pans are reproduced, at least, if a car with good fenders and bad floors turns up.

Fenders bolt on, and the unique body mounts are available. For 1969, GP also had unique paint colors not available on other models, including Code V (Nocturne Blue), Code L (Claret Red) and Code J (Castilian Bronze).

A Strato bucket seat interior with Morrokide upholstery was standard for '69; a bench seat was on the GP menu as part of the WS5 "Turnpike Cruise Group," which meant no console. We've never seen one on a '69 SJ, but it was available. The bench could also have made the 8-track option available, as it was otherwise eliminated by the console. Base seating was cloth and vinyl, with a leather Custom Trim option available.

Upholstery materials are generally available, although not necessarily in all colors and reproduction carpet and headliners are available, while interior trim is hit or miss. Major unique Grand Prix parts like the console and dash are not common, and doing the work is a challenge: "Even taking the radio out is a nightmare," says Ron Panzer. A heater core or underdash work is about as easy setting your own broken arm, and about as painful.

Front and rear glass are also unique: The windshield incorporated the radio antenna, and the backlite was fitted with the GP-exclusive defroster wires.

Mechanically, you're fine, and as long as you don't need a dash there's a good supply of interior materials, and small exterior parts such as headlamp bezels are around. "But there's no serious stuff, like quarterpanels, bumpers or grilles," said California Pontiac Restorations' Richard Plastino. "They're not impossible, but it'll be a love affair project. You're not going to pick up a catalog and start checking items off."

Despite this, there are a couple places to look for GP parts, including Ames Performance Engineering and Performance Years; both are Pontiac parts experts and both include Grand Prix items in their full-size Pontiac catalogs. Both companies are also good sources for NOS GP items. Original Parts Group will have a new Grand Prix catalog around the time you read this, and they promise it will have "many firsts in the Grand Prix restoration market," which is fantastic news.

If you've already upgraded to 15-inch radials, you might want to take advantage of them, and suspension upgrades are a nice place to start. Since the suspension is based on the popular GM A-body, a plethora of aftermarket handling parts are available, including complete tubular control arm systems with matched anti-roll bars from sources like Hotchkis Sport Suspension and Global West Suspension. Traction-enhancing equipment for drag-style competition is also easy to come by.

As we suggested before, if your original or date-coded engine isn't doing it for you, consider stashing it on the side rather than doing something that might blow it up. The aftermarket for Pontiac performance parts has grown tremendously in the last 10 to 15 years, now including aluminum cylinder heads from several sources (Edelbrock, Kauffman) and even aftermarket engine blocks in iron or aluminum (allpontiac.com, Kauffman). You can also source reproductions of Pontiac's coveted Ram Air exhaust manifolds, some with larger-than-stock outlets, available from multiple Pontiac restoration parts suppliers, including Year One.

Both transmissions have proved themselves in performance applications, and aggressive rear ends will go right in.

Owner's view
I was in the Air Force from 1971-'75, and a couple of guys in the barracks had '69 Grand Prix cars, and I thought they looked really, really, cool. I was driving a GTO at the time and I said something like, "Hey, I'd have one of those if they had a four-speed," because I wouldn't drive an automatic. I looked and I looked and I looked--it took years to find one that was actually for sale with a four-speed.

It was a money pit--but on the other hand, it was probably one of the coolest cars I've had.--Dave Schultz

Club Scene

Pontiac Oakland Club International
P.O. Box 539
Victor, New York 14564
Dues: $31/year • Membership: 6,500

What to pay
'69-'70 Grand Prix SJ
Low: $7,500
Average: $15,000
High: $25,000

Parts prices
Bucket seat upholstery kit (complete) $465
Carburetor rebuild kit (428 & 455) $27
Cluster gear (M21) $249
Exhaust (2½-inch, complete) $439
Fan shroud (fiberglass reproduction) $135
Fuel tank (reconditioned) $207
Ignition switch (tilt column, NOS) $49
Main bearing set (428 & 455) $96
Mainshaft (27-spline) $219
Saf-T-Track carrier (10-bolt repro.) $589
Quarter panel and wheel house assembly (used) $850
Starter (high-torque) $209
Tailshaft output seal (TH400) $10
Timing chain, gear set (double roller) $82
Transmission filter kit (TH400) $12
Transmission rebuild kit (four-speed) $189
Trunk floor sheetmetal kit $359
Water pump (remanufactured) $30
Wheel, 15x7-inch Rally II (each) $150


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