How to chop the roof
Street Rod Builder July 2000 has a detailed article on chopping a 39 Ford top. They re-angled the front windshield posts which I'm kind of skeptical about. It may work with flat glass but with a curved windshield, it could cause big problems. Everyone that I talked to indicated that you should keep the windshield post angle exactly the same as the original angle. Section the roof and move the top portion of the front/windshield posts forward to align up. This will ensure that the angle remains the same. Otherwise the Street Rod Builder article is excellent.
The July 2001 Custom Rodder has a howto article on chopping a 53 Chev 3 inches. The big problem with chopping these cars is the curved rear glass. What do ya do with it. They channel the glass into the body.
Rod n Custom March 2001 has a detailed article (step by step pix) on chopping a 59 Buick bubbletop. They didn't cut the wraparound windshield or rear glass. They sliced trenches for the windshield to fit in and also leaned the rear glass forward. You could channel the rear glass into the rear deck possibly? Let the chrome hide the glass...gives the impression that the glass is cut.
Or, check out how much roof top bubble you have. I know that I have probably 3" to 4" of roof above the windshield but its not original 54 though. Could you leave the rear glass in place and lower the roof top to be even and still have good lines? Just a thought.
I talked to a few guys that said that they left the windows the orig height but knocked down the roof lines cause the old 50s cars had lots of head space above the window lines in the roof.
George Barris's book "Barris Kustom Techniques of the 50's Volume I" (ISBN 0-9652005-0-7) is full of examples and pictures of 50s era cars that are in the process of being chopped. Very good descriptions of how the vehicles chopped, channeled and sectionned.
Here's advice on chopping tops that I have received after buying my 54 Pontiac with a 3" chop and trying to cut a windshield to fit.
Chop the top to fit the windshield not the other way around. Cutting windshields is not fun.
Many veteran bodymen and hotrodders have told me that the windshield books will list the dimensions of the windshields. Find one that is close to what you want and modify the body to fit.
Read This BEFORE you chop!
It takes one weekend to chop the top and tack weld it back on. Any fool can do this! It takes a month to finish weld the chop. This is where the quality of planning for the chop shows up. Finally, it can take up to a YEAR to finish the bodywork on a bad roof chop! It took over a year to finish the roof chop on my car. I used two gallons of body filler on it and most of that ended up on the floor - grated or sanded.
Unless you have straight glass for the windshield, side glass and rear glass, I don't recommend chopping a roof - just too much work that takes too much time!
Driver's side view
The above picture shows what will happen if you use the wrong primer and store a vehicle outside for 5 years like the previous owner did - RUST. Fortunately, its only surface rust and looks a lot worse than it is. If you look carefully, just above the driver's door, you'll see the patch panel where the front of the roof was sectionned and moved forward to keep the proper windshield post angle. There's another patch panel in the middle of the rear window opening. You can also see the 53 Chev 150 rear glass that replaced the original curved 54 rear glass. The outline of the 54 rear glass is seen in the weld.
1st Chop Rear Window using original 54 rear glass
2nd Chop Rear Window using 53 Chev 150 rear glass
During the first chop, the roof caved in. I heard it was because the person doing the chop ran a continous bead on the sheet metal creating hot spots and warping the panel. The person who did the 2nd chop, replaced the roof panel with one from the 53 Chev and then ran 1 inch beads every 6 inches to minimize the heat and then hammer welded the panel back to shape.
I finished off the roof welds using a 120V MIG welder and it was very difficult to do. I had no problem with excessive heating at all. I used 0.025" gas wire and a standard mixture of argon/co2 gas. There are only two types of steel wire feed wire: soft and hard. Make sure you use the softer one usually called Super6 or a "-6" in the model number. It is easier to grind and takes less heat.
The roof overlapped the top of the windows for the most part but the two sheet metals were different thickness. I tried to run 1 inch beads but within 1/4" it would burn through the thinner roof material. This was using every combination of voltage, wire feed, hand speed and stickout that I could try.
I found that running a short 1/4" tackweld every 3-4 inches worked the best. Rather than run along the seam, I tack welded across the seam. I alternated over a 2 foot section. My MIG welder was very sensitive to distance from the ground clamp to where I was welding. I positioned the ground clamp close to the middle of the area that I was currently welding. Once you moved about 1 foot away from the ground clamp, you would start burning holes or have other problems. Better control would be nice but that starts to sound like a TIG welder...
There were some places that had gaps of up to 1/4" between the roof and upper windows and at first I tried filling in the gaps using a horseshoe welding pattern with the open end of the shoe facing the gap. This works fine for small holes but I had to fit some sheet metal to fill the hole to prevent enlarging the hole.
Here's a very good tip if you are chopping a roof: Use sheet metal as thick or thicker than the roof for your patch panels. The patch panels above the door and rear window were very thin sheet metal and a real pain in the butt to weld! Also make sure the patch panels are flush and properly fitted. I did a lot of work to fix the poor fit of the patch panels.
I could get away with sloppy welding and no hammer welding cause the roof and the upper window panels did not meet smoothly. There was a dip about 1/2" where it was welded. I couldn't hammer it out because there is a metal frame on the inside of the roof from the original roof still in place. So the plan was to fill it with bondo..
The roof seam has been filled and is being shaped
Lots of work (and bondo) to get the right curve
Notice that the accent line above the rear window has been lost and molded into the body/roof line. The drip rail was removed and the resulting seam was welded also. It was easier to weld cause it had thicker metal. There is a lot of bondo on the C pillar to smooth the rear of the side window. The area underneath the rear window is going to be fun.
I used over 1 gallon of bondo spread evenly over the roof seams to get to this stage. There was hardly any sanding required. I carefully spread out a layer of bondo every day and used a body shaper (cheese grater) to knock off the rough edges. Using the body shaper is nice cause there's very little dust generated. It took about a week at 1-2 hours per day to get it this far. Then I used my DA air sander with 80 grit paper to further shape it. After that I used my electric finishing DA sander with 80 grit to further shape it. Once the sanding started it got pretty messy. Ear muffs and a dust filter are necessities. Safety glasses when using the air sander. Lots of vacuuming after sanding.
Roof lines change from flat curve at front to sharp curve at C pillar
The front of the roof has a shallow flat curve to it. The back has a sharper vertical curve to it. It takes a lot of filling and sanding to make a uniform transition from front to back. It's been good for the arthritis in my shoulders. The first couple of days of sanding, my shoulders hurt something terrible, now they feel great! Got to look on the bright side of things...
The driprail was removed and the seam welded which meant that the detail line had to be hidden
The original photo shows the driprail seam that hasn't been welded yet. Hammer welding to get a smooth weld wasn't possible because there is a support frame on the interior side which is in the way. On top of that the seam is connected directly to the curved window detail. So the only solution is to weld and loose the seam with bondo.
I've circled in red two areas that have given lots of grieve. The left circle highlights the detail at the back of the side window. It is parallel to the side of the car. From this piece that runs parallel, I have to form a gentle curve to the back window. Ideally, when the roof was chopped, this piece should of been curved to follow the C pillar lines. The second circle shows the problem where the detail disappears into the bottom of the rear window. I believe this was caused by replacing the original wrap around rear window with the 150 business coup window. There are two trim lines and the top one has to disappear somehow.
C pillar looks very good!
Here's the roof finished and painted