Hi Roger, as you say the craftsmanship angle is something that I enjoy & I find something very therapeutic about melting lead with a blowtorch and moving it about to get the desired shape. However, as good as modern body fillers are, the one thing that they are not, is being impervious to moisture. A leaded repair will not allow damp or moisture to pass through it, and all factory leaded areas that you see are on joints and seams for this very reason, which is to negate the passage of moisture from the underside of a panel to the surface metal. As you say, you have found "significant structural rust in the steel under the lead",..." Under" is the word here, as if body filler had been used, then the moisture that caused the rust would have found its way between the parent metal & the filler itself, causing the filler to swell & blister on the body surface.Roger King wrote:I'd be interested to know why, apart from the craftsmanship angle, you would choose to lead load rather than use a high-quality modern filler? I have stripped enough cars for restoration which have never been restored before but have significant structural rust in the steel under the lead, so it's not foolproof even from the factory.
The use of lead also allows you to carry out minor repairs to panels, rather than replacing the whole item, or causing additional work through warpage of the steel if you were to try & weld in repair panels, as the heat transfer when using lead is quite low. Using the photos of the sail panels on the Camaro above as an example, there are three options to repair something like that. One is to replace the whole panel, which incorporates a lot of extensive labour time and the cost of purchasing the panels, that's assuming they're available in the first place. The second method is to cut out the rusted area and to weld in new metal. This is likely to cause warpage of the metal due to heat transfer, plus the possibility that there may be unseen pinholes in the welds between the two metals. If filler is applied over pinholes then mositure may be able to travel through the repair & ruin the painjob. Also with a double curvature panel, you'd need to be competent enough to form double curvature repair sections to fit and weld into place. Then of course you have to use bodyfiller over the whole repair to get the shapes correct.
The third option is to lead the repair. This, to my mind is both cheaper and quicker than the first two options and gives an equally good foundation, if not better, to start the paint process. Once leaded, you can forget about it. Another plus is that sometimes when doing body restorations, the vehicle may sit in bare metal for quite some time. If you start to do body repairs with bodyfiller, you will need to seal the repairs up as you go to stop any chance of the filler entrapping moisture. You can't leave a filler repair bare for more than a day or so really. With a leaded repair, you can carry out all of the repairs without having to worry about moisture ingress.
Modern bodyshops are geared for rapid throughput, on cars that are manufactured for a limited life span, so the use of filler to repair them is ideal for those purposes. For repair longevity,on historic, or top end cars, then leading a repair is by far the best route to take.
cheers..Nige
