Saturday, October 20, 2012

Axle Tunnel Filling & Prime

I enjoy momentum on projects.  Once I get into a groove and things start clicking off according to plan, I really like the feeling.  Perhaps it’s the confirmation that comes from planning the work and working the plan when the results are exactly as intended.  Either way, I love the feeling of accomplishment, and lately that’s been a frequent thing.

On the heels of completing the rear wheel tubs, I moved directly to smoothing up and finishing the axle tunnel in hopes I could get it in primer.  As luck would have it, things lines up pretty nicely and I was off too it last weekend with a vengeance.
Early this past spring I was able to repair the rust damaged front trunk floor as well as weld in a patch to fill the hole that was once occupied by the rear staggered shock mount.  Once the metal work was complete, I moved on to repair the rear trunk floors and tail light panel with the intent of coming back to the axle tunnel to finish the area and prime everything at one time.  Well, the time was right to do just that.

During my last sand blasting episode, I was able to get the axle tunnel and trunk floor repair areas well prepped for the coming finish work.  The rear subframes cleaned up very nicely following all of the welding for trunk floors and suspension brackets, and the new rear rotisserie mounts allowed excellent access to the areas around the original leaf spring bushing holes as well.  At the same time, I made sure to hit the weld seams on the axle tunnel repairs to make absolutely sure they would be cleaned of any nasties that might have been living there over the spring and summer.
After what seemed like days vacuuming sand from every conceivable nook and cranny of the car just to keep my shop floor from looking like a beach, I went over the entire axle tunnel with a 60-grit disc to clean it up and give the surface good “tooth” for the All-Metal filler and the Rage finish filler I would use to tidy the area up.

I started my filler work with All-Metal applied generously over and into each weld seam area and rather widely applied filler to each side of the repair.  I like All-Metal for its strength and similarity to lead body solder when working it.  It’s a much more “structural” filler than Rage  and I like it as a base along areas where patches have been welded in but the down side is it’s a bit of a b*tch to sand.
Once the All-Metal base fill was cured for a few days, I drew it down with some 80-grit on my D/A sander and finished the surface with the same paper on several hand blocks.  This gets the contour pretty well established and makes for a very good base for the following coats of Rage filler to get the final contour perfected and finished.

I tend to go kind of heavy on my first coat of Rage to make sure I have plenty to grate off with my cheese grater files.  It makes for a bit more dust on the ground, but I can get the low spots filled pretty quickly that way and not have to come back as many times to get the areas filled.
After an overnight cure, I sanded the first coat of Rage by hand (no DA required or desired) using some of my longer sanding blocks and some 180 grit paper to ensure the surface wouldn’t get lumpy and bumpy.  This would have been a very tedious job if not for the excellent sanding characteristics of the Rage filler.  Awesome stuff.

The third (and final) coat of filler was applied in a thinner and less extensive layer and I tried to keep it as smooth as possible to reduce the amount of sanding required and to keep from messing up the contours I had worked to achieve.  After a few minutes, I grated the surface down and left it to cure overnight.  Then, as before, I started at it by hand with long sanding blocks and 180 paper until I had the surface ready for primer.
With the filling complete, I added the grommet hole needed for the fuel sender wire to pass into the trunk and sanded the remaining surfaces on the bottom of the trunk floor to prep them for primer.  Then, after tacking off the surfaces and swabbing everything with wax and grease removed a few times, I masked the areas I wasn’t ready to prime and tacked everything once more time.

I was pretty excited to try a new spray gun upgrade I added to my gravity feed HVLP gun.  I upgraded to the 3M PPS cup system which makes spraying consistency, paint utilization and clean-up a TON easier.  The biggest plus I find with the 3M system is that I can now paint with the gun in any position (even upside down!) and never miss a beat.  When clean-up time comes around, you pop the liner and cap out of the cup and toss it in the trash.  Then a little wash of the gun head with reducer and you are pretty much ready to go again.  The cost savings in reducer alone will pay for this system very quickly even though the liners and caps are kind of pricey for what they are.  At this point, it doesn’t matter to me one bit as I LOVE this system and will be purchasing the small and medium sized cups for the future as well.
With my new painting weapon in hand and a fresh mix of PPG DP40LF primer in the cup, I laid down two medium wet coats of primer on the entire axle tunnel and bottom trunk floor with about a 20-minute flash time between coats.  Then, I cleaned up what little mess there was, removed the masking very carefully and then shut off the lights and left the primer to cure overnight undisturbed.  The next day I was thrilled with how everything looked and it was quite inspiring to see the entire bottom of the car in one color and looking mighty solid. 

Next on the agenda is to make the small repairs at the front of each rear wheel opening, and a tiny repair to the right rear lower window opening flange, which will mark the completion of all of the rust repairs required on the car!  Whooooohoooo!  Any rust left to address is simple surface rust on the interior surfaces of the body bracing where no factory primer was ever applied.  This will be an interesting application for my trusted chelation rust removal techniques and should work very well.  More to come!
Passenger side rear subframe cleaned up nicely after sand blasting.

Driver side subframe was also in good shape after sand blasting.

I am very happy with the decision to make the new rotisserie mounts that use the rear leaf spring shackle bushing locations as mounts.  This allowed me to blast the entire area surrounding these mounts without a problem.  Should make priming and painting far easier as well.

Here you can see the joint line that I blasted nice and clean before going forward with filling.  I am very happy with how this repair turned out, especially given the amount of rework that was required to get the trunk floor patch panel to even come close to fitting!

After a good going-over with my 2" angle grinder and some 60-grit discs, the axle tunnel was ready for the base coat of All Metal filler.

All Metal filler is awesome stuff indeed.  It is very tough (and therefore tough to sand) but is has excellent mechanical properties and behaves much like lead body solder when finishing.  I love this as a base filler where patch panel repairs are made.

I sanded the All Metal filler with my D/A sander with 80 grit paper to give the next layer(s) of filler good "tooth" to adhere to.

Here is a look at the first coat of Rage filler after it has been knocked down while soft with a cheese grater file.

After hand sanding with long sanding blocks, the first coat of filler is ready to be tacked off and a second coat applied.

The second coat of Rage filler is less extensive and far thinner than the first.  Here, it has been grated down and will be left to fully cure.

And there it is.  Though the different colors of filler make this area look rather lumpy, the actual surface is quite smooth.

One detail I had to add before primer is the grommet hole required for the fuel sending unit wire to pass through into the trunk.

With everything cleaned and tacked off, I masked off the trunk area I didn't want primed yet and started mixing up the DP40LF primer.

The first medium-wet coat of primer is on and after a 20 minute flash time, the second can be applied.

The second medium-wet coat of primer is on and looking great!

Here's a look down the driver side rear subframe rail.  Soooo much nicer than where we started!

A look at the passenger side rear subframe and trunk floor.  Nice!


  1. Wow, that is one big pile of work there Sven! So nice to be able to work on the car in that orientation. Imagine lying on your back and having to pull that off :/

    Nice tip on the paint gun. What a great idea! No paint running down your arm while trying to paint upside down!

    Looking forward to more progress reports!


    1. Howdy RJ! There is no doubt the working position advantages alone are worth the effort to build a rotisserie. I will never do another car again without a trip on the roaster.

      And that 3M PPS gun conversion kicks butt! I wasn't quite sure I would like it, but after 5 seconds of spray time, I was hooked! Now I have to get the medium and small cups and liner kits to round out the set-up (of course!).

  2. Beautiful end result. The sign of a true artist is when you perfect an area that very few people will ever see. Very nice work.

    1. Alex, I am ever humbled by your kind comments. You guys keep me going in this insanity! All the best!

  3. Holy mackerel, Sven! When you say momentum, you weren't kidding. The finished primer product looks awesome. I'm hoping to join the filler and primer club sometime in the near future when I can get some Sven momentum going!

    1. Thanks Dennis! I love it when I can get into a constructive "groove" like this. Even as time comes at a premium! Betcha know how THAT is!

  4. Great work! Curious if you could offer some tips with the Rage filler. I am a novice bodyman, and recently did exactly what you have done to a repair - first all metal, followed by Rage Extreme. But I had the worst time with the Rage! I could not get the set up mix right. It would either harden way too quickly (less than 2 min), or not cure at all. I was following the instructions of putting a ribbon of hardener across the size of the filler. I was so frustrated! I would barely have time to get part of a coat down and the mix would already be hardening. I wasted so much filler and couldn't coat large areas fast enough. Any tips?

  5. Thanks Jay and welcome. Rage in small batches can be a bit finicky about the hardener ratio. I have found myself increasing my minimum mix batch size to about three times what they recommend. In other words, I increase the "golf ball" sized minimum mix to three "golf ball" sized dollops and then apply a thin stripe of hardener across the patch and mixx quickly, but well (even color). There is a picture of my mix volume on a board in my trans tunnel/firewall filling entry last year that describes it exactly. If you can't find it, let me know and I will try to send you the image for reference. Hope this helps!