Like most cars from the late...
Like most cars from the late '30s, David Wrenn's Chevrolet sedan seemed to have too much window area, so it was time to lower the lid on this Bow Tie.
Chopping the top on a vintage vehicle is the big one. It's a modification that requires skill, work, and thinking, but also provides the biggest return in visual change. There are varying degrees of difficulty in top chopping. Take a Model A and most folks can manage a good chop as the roof essentially comes straight down, however, cars became evermore curvaceous, making them both attractive and difficult to chop. Since later cars are filled with compound curves, it takes real skill and serious planning to complete a good top chop.
The subject of our story happens to be a '36 Chevrolet sedan owned by David Wrenn, but the top chopping principles are similar for most cars of that era, as they share similar shapes. The Chevy is being chopped at Rodcrafters in Welcome, North Carolina, with head metalman Larry Shoaf performing the surgery. Preparing the body prior to cutting is very important. If those doors don't fit properly before the top is chopped, they will fit even worse after the chop. Take the time to fit all door gaps and repair any structural damage to the body before making any cuts. Stripping the body of all paint and filler is a big help that minimizes surprises later. Next remove all the glass from the car along with the garnish moldings. The entire interior should be removed and sound damping material should be scraped off the interior of the body.
After being certain the doors...
After being certain the doors fit perfectly, they were removed and cross bracing was installed inside the body prior to any cutting.
With the body gutted it's time to brace the body. Cross bracing with box tubing ensures the body will hold its shape when the roof is removed. Brace carefully across door openings to hold the proper gaps, and remember to allow room for entry as you will be working from the inside of the body as well.
Now it's time to contemplate the cut lines on the car. The first big question is how much do you want to lower the lid? One simple rule is this: cut less, work less. If your chop is moderate, 2 inches or less, the body panels, bodylines, and reveals will line up much easier than a 4-inch chop. Before picking a number, do some math; measure the windows and subtract 4 inches to see how much glass area remains. Windshields smaller than 9 inches can be difficult to see out of, and don't forget to allow the proper amount for gasket intrusion into the field of vision. Some states also have a minimum windshield height law, something to consider before cutting.
While the cut up front is...
While the cut up front is 3-3/4, in the rear a piece of 2-inch tape serves as the cut line. Only the upper cut will be made allowing the remaining metal to bridge the gap at the rear of the roof.
If you simply aren't sure how much is enough, take a good photograph of the side, front, and rear of your car and cut the photo to scale to illustrate how dramatic the changes will be. This also illustrates misalignments caused by cutting. In the end Wrenn decided on a fairly radical 4-inch chop.
Seldom does a 4-inch chop actually measure 4 inches front to rear. In this case Larry Shoaf laid out his cut lines with 3-3/4 being removed from the A- and B-pillars, and only 2 inches being removed from the rear portion of the roof and through the back window. This is done for several reasons. First, the extra metal in the rear will be used to fill the void left by the removed metal, and secondly a roof with a forward angle is more pleasing to the eye, and finally and most important, since the rear of the roof is angled, removing 2 inches of metal from the roof will result in almost a 3-inch vertical drop. The rear of the roof will be lowered and the lower portion of the roof/body will be leaned forward to meet the roof, resulting in an overall drop of about 3-1/4 inches. The B-pillar is the only vertical line in the cut, so removing 3-3/4 there dictates the actual vertical drop in the roof. By cutting the roof in this manner the rear of the roof is allowed to find its own correct location.
The windshield had enough...
The windshield had enough angles that laying it back more was not an option. The posts required virtually no blending for alignment.
The B-pillars were next to...
The B-pillars were next to be cut. Note the rubber bumper on the inner door, keep cut lines away from such items as they help align doors and prevent squeaking.
The final cut was made around...
The final cut was made around the back of the roof area and through the rear window. Only the upper will be made here.