46th Annual POCI Convention ~ Wisc. Dells, Wisconsin ~ June 24-28, 2018
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1972 Pontiac Grand Prix... Convertible

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Owners: Gary and Betty Lee Derner

Vital statistics:  455 Engine/400 TurboHydaMatic, 3.08:1 gears, Air Conditioning, Power Steering, Power Brakes, Power Driver’s Seat, Cruise Control, 8-track tape player, Power Top, 15” B.F. Goodrich Silvertown redline radials on stock Rally II wheels, Midnite Black exterior with Black Stayfast Canvas Top.

Where did you acquire the vehicle?  Vehicle was discovered in the front yard of a former neighbor. It was pulled from 13 years of storage with 50,909 miles on odometer.  The vehicle was jointly owned by two “lil ole ladies”!

How long have you owned the vehicle?  Car was purchased on Dec 2nd 1999 (my 54th birthday) for $2,500 and driven home.

Recap of restoration:  I discovered this car as I was just starting to restore my original ‘72 Grand Prix that we kept for many years soley for that purpose.  But, as fate would have it I sold it to a co-worker  ho ultimately sold it to another party some time later.  During a summer town celebration a few years later I was approached by a young fellow wanting to know if I was interested in buying my old car back before he sent it to the scrap yard.  I bought it on the spot for $50 and the next day I drove it home.  The body was in pretty rough shape but the running gear seemed solid after approx. 120k miles.  I knew this would be a challenge but I was up for it.  I slowly disassembled the car and prepared components for powder coat/ e-coat processes, etc.  for future use.  It was about this time I purchased the 50K mile car that was in real nice shape.  The body required only minor rust repairs with solid floors.  We then decided to use our original car as a parts car as necessary and restore the 50K car.  I was also entertaining the thought of doing a convertible conversion.   The project was then put on hold as we decided to move to a country location and build a house and shop.  Finally during the summer of 2006 I was able to start on my ‘pay as you go’ project.  This would be a frame off restoration so I started the disassembly process. 

The block was sent to a local engine builder and bored .030 over, balanced and dyno’d, but left essentially stock.  I removed the body from the frame and rebuilt the front/rear suspensions, new brake lines, powder coated components etc.  I installed bracing and mounted the body to my spare frame and repaired the rusted areas.  At some point I shared my vision of a custom Grand Prix convertible with my wife Betty.  This was met with a great deal of skepticism.  With my machine shop/tool & die background and many years as a manufacturing engineer, she was confident I could accomplish this but she wasn’t keen on having another convertible.  I had already restored a 1957 Ford convertible that I finished in 1995 and still own and drive to this day. 

But I was determined so she reluctantly went along with the idea.  Me, my son-in-law Mike and grand daughter Hannah traveled to Cincinnati to pick up a ‘72 Olds Cutlass convertible that was to be a major donor.  As it turned out the only useable parts were the ‘A’ pillar header and some of the top mechanism.  Through a friend, I then located a ‘72 Buick Skylark convertible that was used as the major donor.

My first task was to disassemble the top mechanism, sandblast all the components and have them powder-coated.  I then re-assembled with new rivets, washers, etc. that I was able to manufacture in my shop.  A significant amount of OEM hardware for the entire project was sent out for re-plating as well. 

I then decided that the Skylark sheet metal I needed for the conversion was in much better condition than the Cutlass.  It was now time to remove the sheet metal roof.  Initial cuts were made with a Sawzall with the finer cuts made with my air saw.  Betty was not happy and refused to come to the shop for about a week.  I removed the windshield from the Cutlass and placed in the opening on the Grand Prix.  This would be the new height for the convertible header, which was slightly more than an inch lower.  After cutting the Grand Prix ‘A’ pillars about a third of the way down the Cutlass header was cut to fit properly above the windshield, reinforced a bit, and welded in place.

The next phase was to be the most challenging and time consuming.  I marked off the upper rear quarters of the Skylark and the Grand Prix.  I was careful to stay behind the door jambs as to not disturb that area.   The Skylark sheet metal included the upper wheel wells and sub-structure for mounting the convertible mechanism.  An opposing amount was removed from the grand prix including the torsion spring for the trunk lid.  The upper wheel wells were replaced at the seam from the Skylark leaving me the exact location for installing the convertible assembly.  I tack welded the convertible assembly in place and installed the convertible mechanism from one of the donors to check fit and function.  After some minor adjustments I was well satisfied and proceeded with final welding.  I had to be blend the sheet metal from near the door jambs up a short distance on the quarter window area.  The fender tops also needed to be blended to meet the convertible sheet metal.   I contacted a friend and that had a press brake and we formed these as required.

With sheet metal work completed the body was mounted on a rotisserie and sandblasted on the underside.  After a coat of primer I applied ‘lizard skin’ sound material to the inner floors and underside of the body.  Highly recommended as road noise is non-existent.  The firewall was painted Midnite Black in preparation for mounting the body over the finished chassis.  The restored convertible top mechanism was installed and checked for alignment etc.  The black Stayfast canvas top was now installed.   

Many hours were spent preparing the body for final paint (applied by Keith Scheid, former co-owner of Shyd’s Body Shop in New Ulm, MN) on Labor Day weekend of 2013.

Now back to my shop for final assembly of bumpers, windows, trim, interior, etc.  My wife and I finally took our first short trip on June 30, 2014.  Some minor adjustments were to follow but as I write this summary I am extremely confident to drive this car anywhere.                          

What do you like best about the vehicle: The classic lines. This car was meant to be a convertible! 

Do you take the car to shows: A few select shows but mostly roll-ins.  Comments include: ‘I didn’t know they made a Grand Prix convertible”,   “Was that one done in Michigan?”,  “Who did the conversion?”,  “looks like factory”. 

Interesting facts about the vehicle:  low mileage, well optioned, original build sheet and meticulous service records from new.

Future plans for the vehicle:  select local shows and roll-ins.  Planning to display car at POCI Convention in 2015 if possible.

We invite you to join our Grand Prix Chapter!




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2018 POCI Annual Convention - Wisc. Dells, WI - June 24-28, 2018
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