Custom Drop-Top: 1979 Pontiac Grand Prix SJ Convertible
I am constantly amazed by the classics that emerge from estates because the mix is quite eclectic. Take this 1979 Pontiac Grand Prix SJ as a shining example. Someone sought personalization and wasn’t afraid to splash their cash to achieve that goal. The car is no longer a Coupe but an eye-catching Convertible with a matching hardtop. It has some minor cosmetic flaws, although there are no issues that prevent a new owner from enjoying this classic immediately. It is listed here on Craigslist in Bellevue, Nebraska. It could be yours for $25,000, and I must say a big thank you to Barn Finder Tony P for spotting this cool custom.
Pontiac launched the Fifth Generation Grand Prix range for the 1978 model year, following the prevailing industry trend by downsizing its latest offering. The company sliced eight inches from the wheelbase and nearly fifteen inches from the overall length, and it remained a Coupe-only proposition. The Convertible variant disappeared at the end of 1967, but that didn’t stop someone from turning this 1979 Grand Prix SJ into a drop-top. Some cars aren’t natural candidates for this approach, but this Pontiac’s lines carry the conversion successfully. It is unclear whether the work performed by a shop in Topeka, Kansas, includes a soft-top. However, the builders transformed the removed roof into a fully lined hardtop. A close inspection reveals some minor exterior imperfections, but the car’s Starlight Black paint retains a healthy shine. The dark paint shade is ideal for exposing panel imperfections, but no apparent problems are visible in the supplied images. Rust also doesn’t appear to be an issue, while the trim and glass look excellent.
The seller describes this Pontiac’s interior as fully loaded, and there are undoubtedly enough creature comforts to satisfy most buyers. These include air conditioning, power windows, power locks, a remote trunk release, remote exterior mirrors, Rally gauges, a tilt sports wheel, and an AM/FM stereo/CB radio. The interior presentation is hard to fault, with no genuine flaws beyond discoloring on the center console armrest. The remaining Red upholstered surfaces are free from wear, while the dash and pad are excellent. The seller states the A/C doesn’t blow cold but doesn’t mention any other functional issues.
Powering this Grand Prix is a 301ci V8, which the original owner teamed with a three-speed automatic transmission and power assistance for the steering and brakes. The 301 produces 150hp and 240 ft/lbs of torque, propelling this classic through the ¼-mile in 18.1 seconds. That isn’t fast by modern standards, but it deserves some context. The 301 is a relatively modest engine, especially considering buyers could order the last of the previous generation with a 400ci V8 under the hood. It produced 180hp and 320 ft/lbs but could only muster a ¼-mile ET of 18.4. The secret was in the curb weight. The 1977 Grand Prix tipped the scales at 4,131 lbs, but this car should weigh 3,481 lbs. Pontiac’s diet and downsizing bore fruit, with the V8 not tasked with moving so much mass. This approach indicates how manufacturers sought new ways to offset the power losses caused by emission regulations. The seller is sparing in their details about this Pontiac’s mechanical health, not indicating whether they hold information confirming the originality of the odometer’s reading of 27,000 miles. There is no information on how the car runs or drives, but the impression is positive.
This 1979 Pontiac Grand Prix SJ won’t appeal to everyone, but that is true of almost any classic. However, it shows promise and could be ideal for maximizing summer fun. Placing a value on a vehicle of this type is virtually impossible because modified cars write their own rules. It will be interesting to gauge your feedback and see if we have readers who might consider pursuing it further.
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Comments
That’s a Pontiac 301 4bbl under the hood. I like it, and now that we have access to weather radar on our phones, I would use it when I could. With a tarp and bungee cords in the trunk, just in case, of course…
Thank you so much for the feedback, Big_Fun. I debated that one slightly, but I agree with your engine assessment. I’ve amended the article to reflect the slightly better performance figures produced by the 301. I hope you continue to enjoy our articles.
You’re welcome, Adam. All of us enjoy your write ups.
Interesting that the ad says 305. That was only in high altitude or California. I’ve owned a ’79 Regal with a 301 2bbl and another with a 305 4bbl, the latter from California.I found this chart with the engine choices for 1979 …
This actually looks great as a convertible. Very well executed. I wonder what additional bracing was done. If it was cheaper, and there was some actual bracing done, it’d be a fun car…
The bracing was my initial thought, too. Can you simply lop the top off and go? Yikes! I believe there would be serious structural issues.
Wonder how heavy that hard top is and how it attaches? Seems it might be difficult to get on and off
Not really a convertible as more of a removable hard top
Looks well done and sweet interior
It’s unlikely that the conversion includes a folding top. There simply isn’t room for the folded top behind or alongside the rear seat. There were companies doing conversions back in the day that included a soft top – Hess & Eisenhardt, ASC, National Coach, not sure which did A-body convertibles – and those cars had modified rear seats that were much narrower and positioned further forward to clear the top and side rails.
I would’ve liked to have seen a picture with the “hardtop” installed, but aside from the paint flaw, this appears to be be one cool cruiser! GLWTS!! :-)
That top has to weigh at least 150 lb and it’s awkward to handle, so it probably takes four people to handle and perhaps a fifth person to help position it properly. It’s an estate sale. Maybe there’s nobody left to help.
Once again, something I’ve never seen. Thank you, Barn Finds! Two things. That hardtop is definitely not a one man operation. And the 301 in my ’78 GP was a dog.
Sure is a good looking car with the roof removed. Too bad that convertibles fell out of fashion and production during the seventies.
Hate to rain on the parade, but totally agree with the assessment that the car, beyond likely (without a doubt), doesn’t have a soft top. There’s no area behind the seat for the top (no boot, just the normal area). There’s no area on each side of the back seat for the top irons. Seems like someone simply chopped the top off. Somewhat nicely done (assuming the bottom has been beefed up, but no pictures of that, which seems beyond concerning). Regardless, from a practicality point of view, that makes the car pretty much unusable/useless for most all of us. I guess if you want a parade car, for only great weather days, then this would work. Otherwise, not so much. Anyone that buys this assuming it has a soft top, may have a huge and expensive surprise!
I agree 100%. Quite simply, there is no soft top, and the hard top requires 2 or 3 people to install it, and I doubt that all gaskets will make this car watertight.
How heavy is the hardtop and is there photos of it other than the head liner? Any of the top on the car?
You could always email the seller. I’m sure that he could send you more photos.
Interesting build, but the price seems steep–especially when you can get a factory-sanctioned mid-1980s Riviera or Eldorado (or ultra-rare Toronado) convertible of similar body style for less money.
Holy cowl shake Batman!
I had a ’78 LJ finished in Chesterfield Brown with the “Viscount” leather bucket seat option as a six-year old used car in 1984. It was a pleasant enough car but I can vouch for the 301 V8 (2-bbl) being gutless. The engine was remarkably smooth running and quiet though.
O own a Jeep Wrangler with a removable hardtop. There are provisions to secure the hardtop to the Jeep. I don’t see any provisions to secure the roof to the car.
On the positive side, with the weight of the roof gone, it should help that 301 even more!
I’ll bet that thing is so flexy that it creaks & groans like a haunted mansion.
Thinking it was a racer back in the day was a mistake. They weren’t built for racing and showing out. That goes against the national trend of that day. For cruising it was fine. I personally like the colors but prefer t-tops than a convertible.
This is a really cool conversion , but this generation of mid-size GM cars had really flimsy frames ; I hope they added a bit to prevent any flexing
Looks like the removable top has the rear glass and side quarter glasses with just an exposed edge at the bottom. How easy would it be to break any of those moving that thing around and trying to put it on or take it off ??? They should have at least left a little of the metal beneath all 3 pieces of glass!!
I own an 1980 GP.
The 301 was not quick but I beat a Cutlass 1980 307 same year and a Audi Quarto 90’s.
The 301 was rated as 150 hp and the last Pontiac 400 1979 was like 175 hp.
On paper you would think that;s nothing but when you put a Pontiac 400 in a 1980 Grand prix in place of the 301 it’s a whole different car.
I did and trust me you can run 14s Qt miles easy.