# Leading, when to do it?



## GTO Yeah (Dec 6, 2021)

Apologies if this topic has been covered before, but a quick search didn't turn up anything.

When you guys butt weld two panels together, how do you ensure there aren't any gaps in the weld?

I've learned here that welding body panels has to be done carefully as to not warp the metal (usually by hitting a couple spots and spacing them out), but trying to cover every inch of space seems to be a little impossible without running the weld continuously down the seam.

Is that where leading comes in? It looks like there's some factory leading done to join the quarter to the roof, but I can't figure the reason behind it other than to cover possible gaps in the welds.


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## PontiacJim (Dec 29, 2012)

GTO Yeah said:


> Apologies if this topic has been covered before, but a quick search didn't turn up anything.
> 
> When you guys butt weld two panels together, how do you ensure there aren't any gaps in the weld?
> 
> ...


The roof panel is laid one on top of the other and spot welded together. Then the lead was applied. No different if you spot welded and bondo'd over it. 

Check through the various restoration builds and you will see how panels are welded together. Butting the 2 pieces together and then essentially making a lot of tack welds with the mig welder. Space the tacks so as not to over heat/warp the metal. Then come back and make more tacks in between the other tacks, and keep repeating until you have welded up the 2 pieces. Tack welds then get ground down smooth.


You don't want to do any long stitch welds to fill in gaps as this is where the heat will build up and warp things. Timely process, but that is what it takes. You should also find videos on YouTube that show how to do this.


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## GTO Yeah (Dec 6, 2021)

PontiacJim said:


> The roof panel is laid one on top of the other and spot welded together. Then the lead was applied. No different if you spot welded and bondo'd over it.
> 
> Check through the various restoration builds and you will see how panels are welded together. Butting the 2 pieces together and then essentially making a lot of tack welds with the mig welder. Space the tacks so as not to over heat/warp the metal. Then come back and make more tacks in between the other tacks, and keep repeating until you have welded up the 2 pieces. Tack welds then get ground down smooth.
> 
> ...


My concern is that when you weld like that the length of the car (ie my quarter panel), it's inevitable there will be one or two .5 mm-sized holes here or there. I noticed a few when I was working on the car last weekend, but I might just have to go back with a flashlight and fill the welds in. I thought maybe leading was used as a catch-all for tiny gaps like that.


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## PontiacJim (Dec 29, 2012)

GTO Yeah said:


> My concern is that when you weld like that the length of the car (ie my quarter panel), it's inevitable there will be one or two .5 mm-sized holes here or there. I noticed a few when I was working on the car last weekend, but I might just have to go back with a flashlight and fill the welds in. I thought maybe leading was used as a catch-all for tiny gaps like that.


Yep, just go back and hit those pin holes with another tack to close them up. Using lead would be a personal choice and seldom done anymore. I would not have a problem using a quality filler which are much better today then years past. Modern cars now have the panels glued on, no more spot welding. The glue is as tough as the metal.


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## GTO Yeah (Dec 6, 2021)

PontiacJim said:


> Yep, just go back and hit those pin holes with another tack to close them up. Using lead would be a personal choice and seldom done anymore. I would not have a problem using a quality filler which are much better today then years past. Modern cars now have the panels glued on, no more spot welding. The glue is as tough as the metal.


Good to know, thanks!


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## RMTZ67 (Mar 12, 2011)

I replaced a rear qtr and done it as you and Pj described. Light to catch (most) pin holes and jump my welds till the whole qtr was done...fun fun fun.


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## armyadarkness (Dec 7, 2020)

GTO Yeah said:


> My concern is that when you weld like that the length of the car (ie my quarter panel), it's inevitable there will be one or two .5 mm-sized holes here or there. I noticed a few when I was working on the car last weekend, but I might just have to go back with a flashlight and fill the welds in. I thought maybe leading was used as a catch-all for tiny gaps like that.


I have been a certified welder and owned my own shop for more than 30 years, all the while working on GTOs. Jim's advice is spot on. Using lead over resin would be like using a pencil to write a book instead of a computer.


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## armyadarkness (Dec 7, 2020)

PontiacJim said:


> Yep, just go back and hit those pin holes with another tack to close them up. Using lead would be a personal choice and seldom done anymore. I would not have a problem using a quality filler which are much better today then years past. Modern cars now have the panels glued on, no more spot welding. The glue is as tough as the metal.


My new enclosed trailer was the best one you can buy and all of the panels are bonded. No rivets and no welds. The practice was pioneered by NASCAR at least 10 years ago


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## GTO Yeah (Dec 6, 2021)

RMTZ67 said:


> I replaced a rear qtr and done it as you and Pj described. Light to catch (most) pin holes and jump my welds till the whole qtr was done...fun fun fun.


It's a good thing there aren't any windows in the garage! I have a feeling I'll be spending a lot of time sitting in the trunk shining a flashlight out.


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