Sand blasting the engine bay and filling the RF fender apron seam

Sand blasting and I have developed a love-hate relationship over the last two weeks.  On the one hand, it is probably the nastiest, dirtiest, most uncomfortable job involved in restoring a car and takes a long time to do yourself, even with fairly good equipment and great help (thanks Dad!).  Couple that with the undeniable fact that you will discover sand can get into just about any place a man shouldn’t EVER have sand…….well…….you get the picture.

On the flip side, however, there is probably no better way to get decades worth of crap, paint, sealer and rust off a car’s most intricate surfaces.  This reason alone gave me the motivation to spend about 10 solid hours squirting about 1100 lbs of sand toward the the engine bay of my car inside and out.  What I discovered after the job was done was possibly the biggest, most welcome surprise in the 25 years or so I’ve owned the car; beautiful, solid sheet metal!

To further the enigmatic nature of this car, I was pleasantly surprised to find that many of the “normal” rusted out areas expected on old Mustangs were actually in exceptionally good shape!  Torque boxes, lower shock towers, and front frame rails were all very solid and will require very little work to get into pristine condition.  There is no better motivation!

Once everything was blasted clean, I set to filling the weld seam along the top of the RF fender apron where I grafted the original apron top containing the VIN to the new panel from NPD.  I managed to keep distortion to a minimum during the installation and thus a minimal amount of filler was required to get it into shape.  For filling weld seams, I like to use a product called All Metal from USC.  This product is about 80% aluminum filler and is often used as an alternative to the lead used in leaded body seams (like the Mustang C-pillars).  It spreads fairly smooth but is a bitch to sand.  However, once it’s there it is very strong and finishes like metal.

The final step in this series was to clean up the remaining undercoating on the firewall that sand blasting didn’t remove and then chemically treat the bare metal to remove any remaining rust.  I managed to scrape and brush the remaining undercoating patches clean with little effort and used laquer thinner to clean any residue off before etching. 

For metal treatment, I use a phosphoric acid-based metal prep designed to remove any remaining rust from metal surfaces, etch the metal and leave a crystalline-phosphate surface primer behind to inhibit flash rusting and provide an excellent base for primer/paint adhesion (that’s the white, powdery coating you will see in photos).

The next step will be to clean the surfaces with PPG DX330 Acryli-clean solvent to remove any residues and other schmutz that remains and coat everything in two coats of PPG DP40LF epoxy primer.  This will effectively seal the entire engine bay from future corrosion and allow me to move forward making further repairs to the chassis without worry of having bare metal surfaces constantly at risk.  I learned a lesson here and that was to put everything in primer once a job is complete before moving to the other work, no matter how small the project.  I have been making such wonderful progress getting things repaired forward of the firewall, I almost got too far ahead of myself.  Lesson learned.

As you can tell by the picture, the dust hadn't settled yet when I snapped this shot.  My driveway looked like a beach, but the nice clean metal was quite a pleasant sight.  Dad and I screened and recycled 350 lbs of sand 3.5 times to get this job done and still managed to keep about 225 lbs for future use.  That's about 1100 lbs of sand through my little pressure sand blaster in about 11 hours!

Right side apron area showed absolutely no signs of heavy rust anywhere!  A miracle to be sure!

Left front shock tower and frame rail were also exceptional.  You can see the leftover undercoating on the firewall around the clutch pushrod hole.  I will remove this after I have filled the apron weld seam and used the metal prep solution to etch the bare steel.

Right front shock tower and rear apron looked very good after blasting.  At this point, I was starting to feel pretty good about the ol' girl.



Here's a close-up of the left frame rail where some of the scabbed-on pacthes were welded.  No evidence they were ever there!  I still need to patch the lower rail, but this should be undetectable when I'm done.  Also, I removed the corner brace between the torque box and frame rail before I blasted everything to make room for the frame repairs.  I will re-install the corner brace once everything is complete.



Before setting off to etch the bare metal surfaces with metal prep, I decided to finish the weld seam on the right front apron.  After a thin skim of All Metal filler, the weld seam is ready to sand.  I ended up skimming and sanding it twice to get the surface just right.

Here's a wider angle look at the filler.



With everything sanded down, you can see how little filler remains in the seam.  I'm pretty happy with that!





Since it had been a few days since I sand blasted eveything, I decided to etch the bare metal before trying to clean up the firewall.  This is the result after the first coat of metal prep solution.  The white powdery residue is actually a good thing!



This is a beautiful sight to any classic Mustang restorer!  The lower shock tower "pockets" are in excellent shape with clean, solid metal everywhere.  Another miracle with this car.......



With the surrounding metal treated, the firewall undercoat residue is quite noticeable.

Here again, the etched metal patina in interrupted by the leftover undercoating on the firewall.  Time to take care of that!

After only a few minutes with a sharp, flexible putty knife and an abrasive wheel in a drill motor, the remaining undercoating was gone and clean, bare metal remained.  I degreased and treated the fresh metal immediately with metal prep and the results are an even coating of phosphate on the metal.



Finally, the firewall is clean an prepped for the next step.  Next on the agenda is epoxy primer!