QuestionI am working on a 1979 Ford crew cab roof that has been severely damaged by the previous auto shop restorer that filled the caved in roof with body filler and fiberglass to a thiockness if 1/2". How do I determine to shrink or stretch the metal? In the present condition the roof area is about 20" oblong and is caved in not out, the area has been welded in spots also and worked considerably with grinding ,hammer and probably a torch! Since it is such a large area and I can't reach it all by myself I have asked help by my wife when I will proceed! I would like to save the roof since replacements are very hard to find and I am on a fixed income now and replacements I have found are more than the vehicle is worth.
AnswerHi Rich!...If you would like to repair this roof, first off, I would suggest removing the headliner...That way you can attack it from the underside innitially. This way, you will also be able to see if any of the roof reinforcements have become detatched, either from the original damage, or from this repair....Next, you will obviously need to grind out all of the old body filler....Take it down to bare metal....Being an area of about 20 inches, and 1/2 inch thick of filler, you will definitly not have to stretch the metal...That work has already been done by the damage....But you will most likely have to do some shrinking....This would be done by using an oxyacetalene torch, using a #2 tip, or with a unispotter kit..Try and bring up the metal as close as you can to the original shape, by using a body hammer and/or a dolly...Once satisfied, there will be high spots...To shrink metal, find the highest spot and start from there. Heat the high spot, (using either torch or unispotter) to the color of cherry red, and to the size of about a dime. Once heated, take your hammer, and hit the center of the hot spot, and quench it with cold water immediatlly...You will have to work fast..This will re-align the metal molecules, therefore "shrinking" the metal, and returning it to the original shape...You will need to repeat this procedure, picking the next highest spot, until you are satisfied that the metal is as straight as possible....Once done, you can then start doing your bodyfiller work...Generally, if at all possible, the ultimate is to have no more than 1/8 inch of filler...Also, if a torch and unispotter are not available, you can go down to your local autobody/parts and pick up a "Shrinking Hammer"...Although these are not quite as effective, they will provide some relief....Any further questions or concerns, please write back....Thanks....Dave
