After SO MANY hours spent making the metalwork 'just right', it's almost sad to cover it with filler. The key, of course, is to use as little filler as possible. No 1/4" (or worse) patches that could crack after a harsh bump. No filler on parts that are stepped on - or that take a lot of weight. And definitely, no filler on the truck box floor!
Of course after final sanding, much (or all some places) is removed, leaving only enough to make the primer lay down straight enough so that final blocking presents a perfect substrate for paint.
400 hours seems like a lot. That's 10 work weeks. But if you say 2 and a half months, it doesn't seem that long. Thing is, restoring a vehicle is almost ALL labour charges. While a body shop would charge $100.00 per hour, which would be $40 grand to date, I'm half that. Restoring vehicles and paying retail is cost prohibitive for most people, not to mention having way more into most vehicles than they can ever be worth when sold or insured. I'm happy to help though as I love my side job, love restoring great vehicles and always appreciate a great reason for restoring something for someone.
On the '56 International 4-by, the filler work is coming along. The box was by far the worst of it, but it now has a new floor, is reinforced to way more than factory standards, is completely rust free and getting straighter by the hour, as is the cab.
Filler work on right door. The side had entire bottom portion replaced with new metal -
Filler work on box - a minimum of fill was required due to so much work in metal finishing.
With the extensive metal work nearly completed, it's almost time for some filler work. Now filler (aka Bondo) has had many negatives attached to it, but only because of unscrupulous so-called bodymen who have historically used filler like they are troweling cement, or as a sculptor would use hunks of clay.
To start with, one has to know the MAJOR limitations of talc-based filler products: for one, filler should never be used to "fill" anything - only to smooth the final imperfections after metalwork has been properly performed. Second, talc-based fillers are NOT WATERPROOF - and as such, should never be W usedin an area or space that may get wet, or could hold moisture - and thirdly, it is not structural! It won't "hold" anything together, won't re-enforce anything and will definitely not flex.
For those last 2 items - waterproof and flex - the correct product to use is a fiberglass reinforced product. It comes in both short and long strand mixes and uses plastic resins to bind instead of talc. This product should be used over any welds, to "fill" anything deeper than 1/8 inch or if some partial re-enforcement is required. Again, it's not to be used in place of proper metalwork, but is a key product in bringing that fine metal work to its finished stages.
The other key consideration to filler use is proper panel prep. Many guys will just run some coarse paper over the area (or grinder) and slap on the filler when these products are meant only to go on to properly prepared metal.
First step in preparing metal for filler is to treat any rust with a phosphate rust-converting product. My favourite has long been from POR15, which is a non-toxic phosphate wash. This product converts Iron-Oxide (Rust) to Iron-Oxite - a black hard substance that doesn't spread, which means no bubbles will be popping through your expensive paint job years down the road!
The wash chemically treats both the rust and all the metal for maximum
corrosion protection and adhesion:
Once the wash has sat overnight, it is cleaned off with a solvent wipe, which also degreases,
removes wax and dirt residues and ensures the perfect substrate for any filler work.
The truck is now 95% stripped to bare metal with 80% of the metal-work complete. A few rust patches to do on the cab, then we'll mock it all up and start the filer work, which will likely take up a couple hundred hours of labour....
With the complete stripping, I'm sure at least 100 lbs of old lacquer paint and primer came off!