Trunk Work - 1954 Pontiac
The trunk was wire brushed using a high speed grinder which meant that you go to lie down inside while all the rust and dirt get blown all over you. When the wire brush catches and the grinder gets thrown out of your hands, then you get to do a mad scramble to catch the bouncing grinder if the trigger is locked. Good safety gear is critical as I only got a minor scrape on the arm from a wire brush spinning at 10,000 rpm.
After the trunk was cleaned up, the rusted out spare tire well was removed. I used my air chisel to break the spot welds. Down the road, I plan on switching to a 3" single exhaust with the muffler right about where the spare tire well is.
The old spare tire well was cut out
A steel covering plate was cut out
The plate was MIG brazed in place
Finally, I'll be painting the underside of the new spare tire panel with black rust proof paint then seam seal all the seams and undercoat the inside of the fenders. Then it'll be time to work on the trunk lid.
The Trunk Lid
Originally, there was a wide stainless strip running down the middle of the trunk lid. I've taken it off and have to fill the mounting holes. I'm hesitant to MIG weld or MIG braze the holes as they are in the middle of a flat panel and I'm afraid that the heat will warp the panel. So on to other ideas.
In the old days, they used lead for body work. Now leading is basically soldering and my background is electronics. Back in the late 60s and early 70s, I used to make tube guitar amplifiers as a hobby. I used a 250 watt soldering gun to solder tabs directly to the amplifiers metal chassis. This was a pretty standard way of grounding. The nice part is that the heat from a soldering gun is very local (within a 1/2") and it takes about 600 degF (very little compared to the heat of welding).
140 watt soldering gun
I have a 140 watt soldering gun and rosin core (flux core) solder used for electronic circuits so I thought that I would give it a try. I made some "plugs" to fill the holes out of sheet steel.
Here's one of the holes to be filled
I used a bar magnet to hold the "plugs" in place from the backside
The hole must be sanded to bare metal inside and out in order to solder properly (VERY IMPORTANT!)
The plug is held in place from behind with the bar magnet
The hole is soldered in place using the soldering gun a little bit at a time
The solder is ground down with a grinder
It works surprisingly well and the bond is very strong. I tried pushing out a plug with my fingers and couldn't budge it.
A 250 watt soldering gun would be ideal as a 140 watt gun works but is a bit slow in heating up the metal. I tried a few other methods: propane torch, propane torch soldering iron and a portable butane torch but all had problems:
Propane torch heated too great an area
Propane soldering iron wouldn't heat up hot enough
Portable butane torch didn't have enough heat and oxidized the metal
The propane torch heated way too much of the trunk lid and I was concerned that the heat would warp the panel and burn the undercoating. In addition, the butane torch and the propane torch oxidized the surface and the solder would bead up and not stick even though the solder was rosin core. The propane torch soldering iron would not get hot enough no matter how long I waited.
Soldering Tips
- The metal must be perfectly clean and sanded with 80 grit paper
- The inside of the hole must be clean and sanded
- There are several different types of solder
- Acid core solder - used by plumbers for copper pipes
- Rosin core solder - used for electronics and on my car! (Buy it at Radio Shack)
- Plain solder - add flux to it
- Silver solder - high temperature solder
- Solder comes in different gauges, I happened to have a fine gauge (about 28 awg) around and it worked okay but you are forever unwinding off the roll and feeding it to build up the joint. A heavier gauge of solder with a 250 watt gun would work better.
- Heat up the gun and let a little solder melt on the tip. This is called tinning the tip.
- When you touch the tip to the metal, melt a little bit of solder on the tip so that there is better heat transfer from the tip to the metal.
- Now touch the solder to bare metal that is close to the tip. You want the metal to melt the solder not the tip. You will have to wait a little while for the metal to heat up.
- Once the solder melts, move over a little and solder again. You are moving a hot spot around the metal hole and melting the solder with it.
- Solder a ring around the hole's edge first, this will make it easier to solder the plug.
- The plug will heat up faster and easier because it is a smaller piece. You can solder the complete plug.
- A good solder joint will be shiny, flat and feather on the metal. A bad or cold solder joint will be dull and ball up. Round edges are bad, flat feathered edges are good.
- The joint is surprisingly hard when ground flush with a grinder BUT you MUST wear a dust mask as solder is composed of LEAD.
- Check for hairline cracks where the metal meets the plug and if its not nice, solder over the existing solder. It's very forgiving.
- You can build up the solder as in the above picture and remelt the solder anytime.
- After a while, you should be able to lay down a thin layer of solder just around the edge.
- The solder will bond between the plug's outer edge and the holes inner edge.
- Don't need to buy soldering tips ($$$), use solid core copper wire. I use wire from 16 awg electrical wire.
Primered trunk lid upside down on front seat
Here's the inside panel of the trunk lid stripped to bare metal and primered. It's resting updside down on the front bench seat until I finish working on the trunk area. Once it's painted, I will add some sound deadner to it.