72 TA : New Project

[70-SS/RS-L78]

Steve your best bet would be to find a similar type of thin rubber and urethane it behind the crack, If you just try to
butt weld the crack together the part will break. I have refurbished more then my share of Z/28 and TA covers. The
aftermarket covers did not even come close to OEM.

[njsteve]

Through testing I determined material is polyurethane, the same thing they make ATV body panels, motorcycle fenders and water tanks out of. I dealt with this place over the past few days: http://www.urethanesupply.com/index.html and they were an amazing help. I have one of their airless welders on its way along with the welding rods for the polyurethane material. (there is no adhesive known to man that will bond polyurethane -you must weld it to repair it) Another problem is that it is very difficult to get paint to adhere to polyurethane. They even had a step by step on how to do that! http://www.urethanesupply.com/atvpainting.html Great website. Now we know the reason these valances were molded in color: because there were no paints or additives to make the paint stick to them back then.

[njsteve]

Let me rephrase that, it's POLYETHYLENE not polyurethane. My spell checker went a little wild on me there. Damn computers.

[njsteve]

I purchased a plastic welder from www.urethanesupply.com and had some really good results fixing the original polyethylene front valance

Here is the process I went through which was remarkably easy. These valances are made out of polyethylene and once I figured that out, it was just boiled down to following the directions in the kit and using the right plastic welding rods. This contraption is basically a soldering iron with a special tip that you feed the polyurethane rods into.

The first step of course is cleaning the area as best as possible and the using aluminum tape to hold the cracks together. (The aluminum tape is critical as it is very thick and wont stretch like masking tape will: it holds the crack together tightly) Once that is done you use the hot tool to melt a groove in the crack halfway into the plastic. You then apply the flat face of the iron onto the crack and while melting the base material, you feed the rod material into the melted area. You do about an inch at a time and them massage it in very well. Once you get the entire length done you take a strip of stainless steel mesh and apply it onto the repair and melt that into the repair for added strength (preferably on the back side of the panel). When that is done and cooled off (apply cold water to speed things up) you can turn the valance over and remove the aluminum tape, groove the other side's crack and do the same only without the mesh. The interesting thing about the welding rods is that they have a selection of colors available in this kit due to the fact that it is used mainly to repair kayaks and ATV fenders which are molded in color. Once it is cooled you can sand it down.

The face bar portion was a little trickier since it was very hard to get into the rear part of the crack. I heated up the area quite a bit and placed the mesh and a bunch of extra polyethylene rod into the area for added strength.

The process and the tool was amazingly easy and I just saved an irreplaceable part for about $90 in material and 3 hours of work.

Here's the crack:



After taping and grooving:



Applying the welding rod and melting the stainless steel mesh in to the backside of the repair:



The front side after valance was flipped over and the procedure was repeated:

[njsteve]

The hard part was the broken face bar:



After aluminum taping you can how hard it was to get in behind to affect the repair:



After welding and adding a bunch of extra material and mesh. This area wont be seen once the panel is installed:



After the repair:



And here's the final product. The inside joke about these polyethylene valance is that most T/A guys consider them made out of "unobtanium" since they were never offered as a service part and the only ones out there were the ones that were installed on the cars originally in early 1972 and early 1973. (There was no late 72 as the UAW-GM strike shut down the F-body plant in April 1972 until the 1973 model year) Once these valances broke (and they all did) the dealers replaced them under warranty with the steel version which did not have the upper face bars which really make the nose of these cars flow into the grill.

[njsteve]

I also used the welder to recreate the missing broken sections by gradually building up material until it replicated the original contours. This took about three hours today to get the rough shape of the broken sections.

Before:



After:



Before:



After:

[njsteve]

It's Thanksgiving so I'm hiding downstairs since my wife threw me out of the kitchen. Here are the reproduced sections after more welding, filing and sanding:



And the large crack after the same continued process of file, sand and reapply more melted polyethylene:

[njsteve]

And here's the last stage of the broken face bar's repair. The uneven area underneath is actually the factory clearance cut out for the mounting bolt: