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Rusty C3 Corvette windshield frames can be fixed

How to replace a 1968-1982 damaged windshield frame

Walt Thurn Apr 20, 2018
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Corvettes built from 1968-’82 share the same steel birdcage frame that supports the surrounding body panels. The upper windshield frame is constructed with five major components and each was spot-welded together to form the windshield frame. These various parts include two main pillar posts, the upper header and two reinforcing corners. The pillar posts and the header are constructed from hollow steel and only the outside surfaces were usually painted. If a hole develops from rust in the header, water will flow down the frame and into the footwell kick panels on both sides of the passenger compartment.

Several things—over time—can cause this part of the frame to rust and deteriorate. It is easy for debris and leaves to wedge themselves underneath the chrome trim around the windshield. They hold moisture and cause rust to begin forming on the metal. Cars that have spent their years in wet, moist climates are prone to having large buildups of rust on the surfaces of their windshield frames.

The frames were originally constructed by spot-welding the ends of the pillar posts. Then the corners were spot-welded to both sections. These overlapping joints were never sealed. The windshield frame is covered with metal trim and there is enough of a gap to allow the leaves and debris to be trapped in the channel underneath the chrome trim. It takes a while for moisture in this area to dry out. The most troubling is water will run down the side of the windshield frame and collect in the lower #2 body mount area in wells beside the driver and passenger compartments. Unless these leaks are corrected immediately the windshield frame will rust beyond repair and will need to be replaced.

If you find that your windshield frame is in this condition there are two options we recommend. The first requires a ton of patience and time. This method is to chisel and hammer out all of the spot welds that were used to construct the windshield frame at the factory. In addition, you can purchase a spot-weld cutter at the hardware store. The spot-weld cutter is a center bit with an outer cutting tip built into one drill bit. This will enable you to drill out all of the original welds. You will still have to use your hammer and chisel to cut the frame apart. Corvette aftermarket suppliers sell reproduction windshield frame replacement pieces to restore this critical part on your Corvette. You will need access to a MIG welder and someone to operate it if you cannot perform this task. The second way to make this repair is to let a professional shop like VanSteel perform this work.

The company encountered a non-repairable windshield frame after a customer commissioned them to restore their Corvette. Its windshield frame was so deteriorated it could not be repaired and needed replacement. An undamaged windshield frame was located at a swap meet at a local Corvette show. The VIN (Vehicle Identification Number) was carefully removed from the rusted birdcage and set aside until the repair was finished. Measurements were carefully recorded on a piece of tape so the new frame would fit perfectly. A powered saw was used to cut the old frame out of the car and after about three hours of labor the replacement frame was completely welded in place. The seams were ground smooth and repainted in black to keep them from rusting. The original VIN number plate was installed and the new frame looked good as new. So if your Corvette birdcage is badly rusted, take heart that it can be repaired. Vette

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1. A customer commissioned VanSteel to restore his Corvette coupe. The restoration included refurbishing the frame, body and interior.

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2. All C3 Corvettes, from 1968-’82, were fitted with this steel birdcage. Body panels were bonded to this frame to hold them in place. The convertible birdcage did not have the T-bar or the rollover hoop behind the driver and passenger compartment. The rest of the structure was identical to the coupe.

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3. When VanSteel removed the windshield and trim this is how the badly the windshield frame was rusted. Rust had weakened the entire structure and it had to be replaced. If your windshield is unbroken and free of nicks you have three choices. Leave it alone, take it out yourself or let a professional perform the task.

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4. Measuring the existing frame is a critical step in the replacement process. A test windshield was set (not secured) onto the frame to add shape and minimize flexing.

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5. The best way to measure a convertible frame is from the rear bulkhead to the top of the windshield frame. On coupes, measure from the edge of the rear roof to the top of the windshield frame. You also want to measure from the floor to the top of the windshield frame for both coupe and convertibles. Remove the test windshield when the measurements are completed.

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6. Besides putting the measurements in a notepad for future reference, they were scribed onto pieces of tape and placed on the left and right side of the body near the work area. This is a secure way to remember any variations between the left and right side of the windshield frame.

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7. Use a saw to cut through the windshield frame on either side of the T-bar on coupes. The T-bar support will need to be chiseled off once the remainder of the windshield frame is removed. This step is not necessary on convertibles.

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8. The remainder of the old windshield frame needs to be removed to gain access to the welds that hold the T-bar support to the windshield frame. A saw was used to gain access to the T-bar welds that hold it in place.

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9. Once the T-bar welds are exposed, a rotary grinder was used to grind the welds so the old frame could be pried off the T-bar.

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10. This used windshield frame was found at a Corvette swap meet and was in excellent condition. It even had the VIN number plate attached. However, it was removed and discarded. The VIN plate on the rusted frame will be removed and reattached to the replacement frame.

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11. The replacement frame was measured against the existing frame to ensure ample room was available prior to cutting the old frame off the car. The new frame extended below the lower weld joint and this joint was selected to saw and remove the old frame.

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12. This is what remains of the old frame after it was cut off of the remainder of the birdcage.

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13. The T-bar attachment is carefully removed from the replacement windshield frame. All remnants of the T-bar mounting must be ground away in order to fit the parts together successfully.

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14. Use clamps to hold the replacement frame in place and compare your measurements from the original frame. Make any adjustments before welding the frame in place. It is a good idea to tack-weld the frame so you can recheck your fit. It is a good idea to lay the test windshield into the frame to confirm the fit.

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15. Once your measurements are confirmed, remove the test windshield and line up the T-bar with the windshield frame. It is a good idea to tack-weld everything first so you can recheck your fit.

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16. A long clamp is attached to the windshield frame with an extension down to the rear bulkhead. This keeps the frame from moving during the final welding step. Once everything is rechecked, complete the welds.

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17. The test windshield and T-tops were set in place and the frame was re-measured to confirm everything fits correctly. The measurements were the same on this car.

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18. Once the paint and bodywork are completed the windshield and trim were installed. The trim along the top is held in place with 8 to 10 clips. The side trim on the windshield frame is held in place with Philips screws.

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19. The completed windshield frame is free of leaks and with proper care should be good for many years of trouble-free ownership.

Photos by Walt Thurn

Sources

CarTech Books
North Branch, MN
800-551-4754
CarTechBooks.com
VanSteel
727-561-9199
www.vansteel.com

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