Rear Valence & Trunk Lid Fitting

First, I offer my apologies to the followers of this blog for yet another long period of silence between updates.  Sparing the details, it’s been a rough past six weeks for our family and it was time to take care of our own for a while and, as such, the Boss project rested patiently until things calmed down enough to resume.  However, I am VERY happy to say that there has been some fantastic progress in recent days and a good bit more to come in the next few weeks.

As I have mentioned in past posts, I like to begin the body fitting process from the rear of the car.  The main reason for this is the rear quarters are the “anchor” panels that every other panel eventually keys off of for final position.  Therefore, it is critical the back end of the car is tight and right before moving forward with other panels.

Having finished the “basic” bodywork on both rear quarters, I was able to concentrate on fitting the rear valence panel and getting the end gaps just right, followed directly by fitting the rear deck lid.  But, first things first…..

About 25 years ago, I managed to get an NOS rear valence for the Boss and squirrel it away for the time when I would fit it to the car during restoration.  So naturally, I figured this would be the perfect place to start actually fitting a body panel to the car as it would probably be a slam dunk for fit.  WRONG!

The more I tried fitting the stock NOS rear valence, the more I didn’t like it.  It was rather poorly made overall, the edge finishes were crap and the edges themselves look like they were formed with a baseball bat.  Complicating things further, the panel width was roughly ¼” too wide for the car!  So, after a short debate with myself on what to do, I added a reproduction valence to my NPD shopping list and moved on to evaluate my trunk lid options.

I have to admit, I was only marginally confident that my production trunk lid was going to be usable after all of the abuse it had endured and the rust it had accumulated over the years in the corrosive South Texas Gulf Coast air.  The first thing on the evaluation agenda was to bead blast around all of the perimeter flanges to see how solid they were.  Much to my surprise, they were all in excellent shape after a moderate round of blasting.

However, when I switched my focus to the “beauty” surface of the deck lid, the wheel rather quickly fell off the wagon.  In only a few minutes of light blasting it became painfully evident I was not going to be able to use this lid as there were about 6 significant pinholes that were revealed when each of the heavier rust freckles was removed by blasting.  Instant game-over as far as I was concerned.  Another significant addition to the NPD shopping list and plenty of justification to make a trek to their Canton, Michigan warehouse for a parts run!

After carting my new, virgin sheet metal home, I set about evaluating the fit of the new valence with excellent results.  Although rare in my experience, I am happy to report the reproduction valence fit miles better than the NOS piece ever did and made for much less work in order to get the corner gaps fixed to my liking.  Not a bolt-on by any means, but pretty darn close in comparison to the stock panel for sure!

After a solid day of fitting, grinding, fitting and grinding, I was able to get the end gaps looking very sporty and infinitely better than 90% of the restored examples you regularly find.  Once I got the gaps very close to perfect, I sealed the edges with a careful application of silicon bronze along the entire “worked” edge to ensure there would be no compromised edges on either end of the panel.  Then I cleaned up the edges with a surface disk and indexed the panel to the body to ensure I could always repeat the fit each time I needed to remove and reinstall the panel.  In the end, a thin application of filler to the joint area and the valence ends will be able to be perfectly mated to the body contours.

Next up, it was time to test fit the new reproduction deck lid I picked up.  Om first blush, the panel is a very nice quality stamping with features almost perfectly mirroring the stock lid.  In fact, for 90% of the restorations out there, it will likely be as close to a bolt-on affair as can be expected.  However, for the demands of a project like this, I knew there would be many hours of work required to get it to fit at a much higher level of precision.

After quite a bit of manipulation and adjustment, I actually managed to get the side gaps almost perfectly where I wanted them and the lid fitting surprisingly flush around almost all edges.  However, the leading (front) edge of the lid had a rather massive gap that simply could not be remedied with any amount of adjustment.  The bottom line was that there simply wasn’t enough material along this edge to achieve a proper gap and the remedy was to employ the rather standard custom car practice of adding material to the leading edge of the lid to close up this gap enough to allow careful hand-fitting of this edge to the trunk opening so that the cap could be much tighter and precise.  But, before diving into that work altogether, I just had to mock up the tail of the car just to get a look at what it will look like all assembled.  And what do you know?!  It actually looks like I might just have a bloody CAR after all and most indications suggest it might just be a 70 Boss to boot!  We are back on the move!

This 25+ year old NOS rear valence was supposed to be the hot ticket to start the rear panel fitting.  Unfortunately, I didn't like how rough the finish was one each end and how poorly the fit was overall.  Didn't take long to decide to pick up a new reproduction valence to see how the two would compare.

Straight out of the box, the new NPD-supplied repreoduction rear valence was miles ahead on fit over my old NOS piece.

Still a bit too wide overall, but the new reproduction valence will work quite nicely.

Left side was the better fit, but both sides will be getting the custom gapping techniques applied.

Like almost every Mustang rear valence, these punting bracket tabs will need to be cut back beyond the edge to allow proper gap work to continue.  The cut lines are marked in yellow paint pen in this shot.

First steps in establishing proper gap create a slight separation between the rear quarter corner and the valence.  Already, the fit of the panel looks far better than the bolt-on fit.

A little more work on the right corner and things are starting to shape up nicely.  Still a bit tight, but definitely better.

Left side corner is also tight to start but quite a bit less work will be required on this side to get the gap correct.
 

After sealing up the edge of the panel with a bead of silicon bronze weld, the gap is hand dressed to the perfect width, creating a subtle, yet unmistakable fit quality that no factory Mustang enjoyed.

My old factory trunk lid conspired to disappoint when I discovered about 6 small pinholes in the outer skin as a result of the murderously caustic South Texas salt air environment.  Dammit!  Luckily, the much-improved replacement trunk lid from NPD proved to be a worthy replacement and will involve far less work to fit to the body than the repaired original would have allowed.

In the mock-up phase, I add a strip of masking tape to help visualize the overall end cap and trunk lid alignment.

I was genuinely surprised at how well the new trunk lid fit right out of the box.  Deck lids on 69-70 fastbacks are quite finicky to get the gaps right as it is, but the NPD lid, while not perfect, is a very nice piece of business.

Factory hinges and adjustment range allowed the right side edge gap to be almost spot-on with no modification.

A little extra time in adjustment had the left side gap quite acceptable as well.

The gap at the leading edge was another story.  While it rather accurately reflects the wider gaps in this area of a factory panel, the look is just not something I can live with.  We will need to close up this gap to the standard 3/16" spec with quite a bit of work that will be covered in the next installment of this blog.

I just couldn't resist the temptation to see what the rear of the car might look like with all of the panels in place.  For the first time in YEARS I can actually see that this is a 70 Boss Mustang!

Right Rear Quarter in Primer!

Quick on the heels of completing the bodywork on the right rear quarter, I wanted to get the right quarter safely coated in PPG epoxy primer so work could smoothly progress.  Recalling the complicating events of priming the left quarter, I was a bit hesitant to dive into the work as I was not sure what equipment issues I may encounter.

However, save for a few relatively minor glitches, the priming work consumed the better part of a Saturday afternoon anchored by near perfect weather.  Humidity was low and the temp in the high 60’s with almost no wind to stir up little nasties.  And after a thorough round of degreasing, I started the process by masking everything I didn’t intend to prime.  Learning a bit from the left side work, I was able to get good masking coverage with much less material than before without sacrificing any protection.  Bonus!

Another rinse with pre-prep solvent and about an hour of dry time had the surfaces ready for a cut-in and thin base coat of primer.  An hour of flash time, and a second coat was applied and allowed to dry overnight.  The end result was rather pleasing as everything was finally in a single, uniform color and the true contours of the panel were finally visible.  Fortunately, save for a few pinholes in a few spots of filler, the surface will block out perfectly after high-build primer application and we will be in business!  A few days to allow the primer to thoroughly harden will be in store as preparations begin to fit the lower valence, quarter extensions and the rear deck lid.  Once this work is complete, things will start getting interesting pretty quickly as the car starts looking more like it should! 

Right quarter in full primer is a nice sight to behold.  Arguably, this is one of the best angles of the 69-70 Mustang body form.

 

With clean fender lip lines and crisp body creases, this view begins to show how nice this quarter will look when fully finished.

A very subtle and often missed detail is the upper trunk opening corners.  The filled seam is clearly visible in this shot and I love the look!

 

Another look at the front trunk lid corner opening smoothed and primed.

 

And finally, a nice look at the roof seam area of the sail panel.  perfect flow with no hint there is any joint in this area.

Smoothing Up the Right Rear Quarter

As I mentioned in earlier posts, the right rear quarter panel on my car was the most in need of metal work and filling as any other panel on the car.  However, knowing this going in, and coupled with a good plan of action, this heavily iterative and time consuming project went quite smoothly and the results reflect the effort.

As outlined in my post covering this process on the left quarter, I start by sparingly applying the “heavy” filler in all of the areas that have welded seams or require more robust filler as the base to build on.  I use a product called All-Metal for these areas as it is as close to a metal (more specifically body solder) behavior as any polyester filler available.  It has excellent sealing characteristics over clean welds and although it is rather demanding to sand, it can be feathered and smoothed rather well and provides an excellent base for the primary filler I use.

Once the All-Metal is sanded to shape, the process of applying thin coats of Rage Gold body filler begins.  Generally speaking, the first base coat of filler I apply is the heaviest and every subsequent application gets thinner and thinner and over smaller areas until the panel is straight.  There is simply no possible way (other than pure luck) that the filling and smoothing process on a show-worth body will be achieved in a single pass.

After each layer of filler is applied, I knock down the ridges and rough shape the surface with a Surform tool.  One thing I take the time to do is smooth up the fender lips such that they are much more presentable than the often nasty surfaces presented by the factory work.  This also helps create nice, clean wheel opening lines that really look sharp when done.

I will often use my DA sander with 80-grit paper to shape the first layer or two of filler as this is often just a way to establish a base to work from and not the final finished surface that will be established by hand.  This also provides a very nice platform to apply powdered guide coat and block the panel by hand just to see the first indications of how and where I will need to work the most.  From this point on, every successive pass with filling and blocking will be done with guide coat and a very careful application of DA and hand sanding until the final shape is almost complete.  At that point, absolutely ALL of the final blocking is done by hand and with many coats of guide coat to indicate progress and panel accuracy.

Because I had a lot of area to cover that would need various levels of work, I split the quarter into 3 work sections and tackled one section at a time.  I started at the rear where the highest concentration of welded repairs were required and smoothed up the entire rear half of the quarter in the first phase.  Then, with that zone completed, I moved to the front half of the quarter and repeated the repair process until the results were as perfect as I could make them. 

This was an area that was particularly complicated in that the amount of filling that was required was very thin but in many spots that simply were impossible to detect with the naked eye or even by hand.  This is where the religious and generous use of guide coat is the only way to get this type of area straight and actually saves tremendous amounts of time in the process as well.

The final zone was the “top” of the quarter and involved essentially two areas of interest:  the trunk corner seam and the roof seam at the sail panel.  These are rather curvy locations that require very careful and slow sanding to get the contours perfected.  The roof seam area also represents the heaviest filler application anywhere on the car due to the recessed seam area once filled with factory applied body solder.  However, the technique is pretty much the same here as it is anywhere else, and the generous use of guide coat will pay huge dividends along the way.  In my opinion, this sail panel area is one of the sexiest areas of the 69-70 Mustang body with the long, deep curves running almost the full length of the quarter.  That’s hot!

So, now that the right quarter is smoothed up, the next steps will be to prep the panel and quarter end caps for masking and then shoot the works in a coat of trusty PPG DP40LF epoxy primer.  Once that is done, we’re off to the next panel!

First bit of filler than I apply is All-Metal and is used to seal any welded patch area or any area that required welded pins to pull damage.  This filler is very hard and works more like body solder than Rage Gold so I use it sparingly to provide a base to work from.

Shaped & sanded with 80 grit paper to rough out the shape and we are ready to apply standard body filler for the rest of the job.

Here, you can get an idea how thin the All-Metal filler is when dressed down.  Maximum thickness in any spot is only on the order of .050".

Both the rocker panel welded seam and the area where the crease was removed get a thin coating of All-Metal.  These areas have been sanded and are now ready for a very thin skim of Rage Gold to finish.

A thin skim of All-Metal filler is applied to the seam welded joint at the base of the rear windshield and sanded smooth with 80-grit.

The first coat of Rage Gold is rather heavy with the understanding and intent of seeing most of it deposited on the floor as dust, leaving behind a very solid foundation for subsequent filler application.

I regularly employ Surform tools to shave the filler to rough shape just after the filler kicks to the heavy gel phase.  This is a bit like hard cheese and shaves very easily with these tools.

In the early filling stages, I rough out the initial shape with 80 grit paper on my DA sander and then finish the job by hand with various sanding blocks.

I absolutely LOVE dry powder guide coat!  Not a single layer of filler avoids a generous application of guide coat to allow me to easily see the shape and accuracy of the panels before, during and after sanding.  While the camera flash makes the guide coat look very light, in practice, these filler areas are stained quite dark and provide huge contrast when sanding.

Finishing body filler by hand is the only way to get things dead flat.  In this shot, I am sanding in an "X" pattern, starting at the top right of the panel and moving down to the bottom left and then reversing the direction, beginning in the top left and ending at the bottom right.

Having started at the back of the panel, I finished the rear half first, before moving to the front of the panel.  This shot shows several iterative layers of filler were needed to get the shape I wanted in the early stages.

The bulk of filling work at the rear of the quarter has been completed in this shot.

The final bit of work on the rear of the panel was fitting the panel contours to the die cast fender end cap.  The fit of these panels can be all over the map and this one required a bit of extra work to get the contour just right.  The green masking tape prevents body filler from sticking to the end cap while I apply it to the quarter.

Once the filler reaches the gel phase, I use a razor knife to cut the filler along the thin gap between the quarter edge and the end cap to create a straight line that is much easier to finish.  Once this bit is fully cured, We sand the filler to the proper contour and get ready to tackle the front and top of the quarter.

Like the rear of the quarter, the front is prepared in the same iterative way as all of the other filler work I have shown.  Thin applications of filler and careful sanding with guide coat allow the panel to flatten out very nicely.

And there we are!  The front and back half of the right rear quarter are complete.  All that remains is the roof seam at the top of the sail panel and the rear trunk corner.

With the first application of filler on the sail panel, I start by shaving the contour to the rough shape I want using a Surform tool and sand to shape with 80-grit paper in the DA sander.  This first coat is just a bulk-filling application as this joint between the roof panel and quarter is quite deep by design and requires a good bit more filler than most any other place on the body.  Recall in an earlier post that this seam had already been filled with All-Metal to seal the weld seam and fill the body solder trough.

The second application of filler to the sail panel is much thinner than the first.  We are getting very close to the final surface.

Shaved with the Surform tool and ready to be carefully sanded to final shape.

About 4 passes with Rage Gold filler were required to get the sail panel joint perfected.

Dent Repair & Metal Finishing on Right Rear Quarter

A month has passed since my last update, but activity has been steady and productive as the adventure begins on straightening the right rear quarter panel in preparation for filler and primer.  And with the exception of another week of international travel for work as an interruption, I have been working on the car pretty steady for the remainder of time.

In contrast to the left rear quarter, the right rear quarter had seen significantly more abuse over its lifetime.  In fact, some of the metal repairs that would be required were actually to reverse the effects of botched metal work that had been done in excess of thirty years ago and I was actually able to identify a shopping cart impact that left the front of the quarter clearly indented with perfectly symmetrical vertical divots from front to back.  Further to that, I had a deep crease in the lower front apron area and quite a bit of damage to the leading edge of the “hip” area at the front top of the panel.  Plenty of work to be sure!

First things first, however.  A huge benefit of the right quarter was that the spots of surface rust were far fewer than on the left.  This made scrubbing them away with a surface prep disc on my angle grinder a relatively quick affair.  As expected, there were several tiny areas where some micro-pitting was evident and I marked each of these areas for later attention from the Speed Blaster.

Once the surface rust was gone, I went over the entire panel from front to back with a clean 36-grit disc on my DA sander to clean up and prep the panel for a swab with diluted Prep & Etch to preserve the bare metal as the work progressed.  Then, I set about tackling the top section of the quarter where earlier work had been done (and quite poorly I might add) as this area would present some unique challenges to getting the metal straightened.

To begin, I used my giant Sharpie marker to stain the repair area so I could block over the surface to identify and clearly highlight the damaged area details.  This actually revealed a much more extensive and complicated repair area than I had estimated, but the details were clear and the path set to get going on the repairs.

Starting with my bulls eye pick, I slowly started raising the low areas along the roughly 20-inch gouge in the panel as well as the palm-sized dent in the “hip” and a significant ripple along the forward character line.  This is a very iterative and slow, painstaking process that rewards patience and gentle persuasion.  Slowly, the metal started to gradually move back into place and after several cycles of staining and bumping, I reached a point where I would need to use my stud welder/puller to remove the deeper section of the crease.  After several hours this process, the areas was returned to within 98-99% of its original shape and I could move on to the next repair areas, until all of the metal work was complete.

The next step was to return to the slightly pitted areas I had earlier marked so I could ensure every trace of rust was removed by using the spot blasting nozzle on my Speed Blaster tool.  This nifty tool allows me to very quickly and cleanly spot blast each small spot of pitting, leaving rust-free, clean metal behind.  This few minutes spent ensured I would not have issues with future re-development of rust in these areas and contributed to considerable peace of mind as well.

With the spot blasting work complete, I once again sanded the entire panel with 36 grit paper to establish a clean surface with sufficient “tooth” to allow the “heavy” All-Metal filler to be applied to seal the welded areas, and to allow the formal body work to begin.  By the time you read this, that work will be well underway!  Stay tuned!

Surface prep discs were used to scrub away the bulk of the surface rust spots on the quarter.  Far less work involved here than on the left quarter for sure!

The upper "hip" area of the quarter had the remnants of a poor attempt to push out a heavy crease that ended up with surface rust in it from end to end.  The lighter gray area above and below the long strip where I scrubbed the crease shows the huge shallow dip along almost the entire front section of the hip.  This is going to require hours of metal finishing to get back in shape.

This lower apron area also had a major crease along it's full length that ended in a nasty cleft in the leading edge of the flare.

After all of the surface rust areas were scrubbed clean, I went over the entire quarter with my DA and 36 grit paper to smooth up and clean the surface to bare metal and to provide the ever important "tooth" to the metal required for proper filler adhesion.

Fortunately, only a little metal work was required on the top of the fender to get it into fine shape.

Using my trusty big Sharpie marker, I marked the entire damaged area of the hip so I could start sizing up the extent of the metal work that would be required to get this previously repaired area back into shape.

A few light passes with the sanding block and the damage was revealed.  Essentially, the entire area was one huge low spot with more heavy damage concentrated along the middle of the crease and lower on the front hip area.  These more heavily damaged areas are easily seen in this shot as they are the spots still colored in black marker.

After a few short minutes of work, the metal is starting to gradually move back into place.  However, there are many hours left to get this area corrected.

In this shot, most of the front hip area has been bumped back into shape with only small detail work left.  Notice how little black marker ink is showing in this area.  It is quite obvious I am working from front to back in this particular area.

The front hip metal work from a slightly different angle. 

As I moved back into the heavy crease, it became obvious I would need to gently pull this damage with my stud puller in order to get the metal to move enough to bring it up to the proper level.

After about 6-8 hours of gentle metal persuasion, the upper fender is pretty darn good.  It will need a very thin skim of filler to get it perfected, but that is pretty straight nonetheless.  Also, I have worked out the lower apron crease and a few other smaller flaws I found along the way.

For an extra measure of insurance, I chose to run over each former surface rust location with the spot blaster to make absolutely sure there would be no rust remaining in the metal pores.

Looks like the quarter panel came down with a case of the measles after spot blasting.  In this case, it is a very good thing!
 

 

Cleaned up with another pass of 36 grit paper on the DA and the quarter is looking much better than it did when I started!

After sanding, you can just make out the shadow of the heavy crease that once occupied this area of the upper quarter panel.

Rear of the quarter after metal finishing looks quite good.

 

And there it is!  The right quarter is ready to begin the slow process of filling and blocking on the way to a sealing coat of epoxy primer.