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Hello from the shop fellow bloggers & hard-core auto restoration enthusiasts!  I wanted to personally invite you to visit and "Like" or "Follow" our Night Mission Boss 302 pages on Facebook & Instagram.

We post short progress updates more frequently at these two social media outlets.  It's a quick and easy "on-the-fly" way of keeping the information flow on the project coming your way!  So please feel free to visit our pages and drop us a comment or two and if you like what you see, please "share" our pages with your friends!

Thanks!

Sven

Rear Body Detail Work & Hi-Build Primer Application

They say that “slow and steady wins the race”.  However, for a guy who has been in racing and performance cars all his life, THAT is a very LARGE pill to swallow.  A pill roughly the size of a men’s size 14 Reebok Hi-Top in fact, but as wiser men than I have counseled over the years, patience will pay off and I trust in that.

With the end cap gaps set earlier on, it was time to invest a few hours leveling the remainder of the end cap surfaces.  Oddly enough, these die cast alloy parts are actually very wavy and rippled and require quite a bit of massaging to get them smooth and contoured correctly.  In fact, just about every surface of these parts requires a thin application of filler and repeated blocking to get them straight.  Fortunately, the end caps I have were reasonably good and very little filler would be required to get them in top shape.

Next, with end cap and valence gaps looking very tight, a few hours was dedicated to getting the forward edge of the trunk lid gapped exactly as I wanted and the contour matched to the trunk lid.  Since the trunk lid and lower rear window panel will maintain the classic Boss 302 trait of flat black paint, these edges need to match well to not look out of place. 

With very thin applications of Evercoat Ever Gold glaze, the surfaces and edges of the trunk edge were brought up to match the trunk lid edge very well.  With a bit of hi-build polyester applied, these areas will be able to be perfected with careful block sanding.  Also, I permanently glued specially machined spacers to each end cap mounting stud that ensure a precise gap is maintained.

Following the end cap work, we transitioned to the task of tidying up the flanges that mate to the quarter end caps.  As stampings, these surfaces were anything but straight and flat and the factory made up for this by using a thin rubber gasket between the end cap and quarter.  Since these end caps have been custom fit with a thin gap, these gaskets no longer work (or even exist) in the project.  So, extra time must be taken to carefully fill and flatten these flanges to ensure the finished gap is straight and even from top to bottom.  Yep, more work that you will never see, but the end result is what it’s all about!

The focus was then shifted to clean up the flanges on the back side of the rear valence to ensure the panel gap is properly presented and the edges of the panel are clean.  I prefer to use a product called Duraglas by USC for this type of work as it is completely water proof and works very well as an edge reinforcement with its fiberglass-strand reinforcement directly in the mix.

The final detail work to be completed before masking for hi-build polyester primer was to smooth the rear fender arch flanges to complete the look we are after in the detail areas.  Most factory Mustang fender flanges are nasty bits of jagged metal and lumpy spot welds that look awful with even the finest finish applied.  A lot of cars have fender opening trim that somewhat hides these flanges, but Boss 302’s never had that crap on them and therefore, these had better look tight!

Moving forward, the time had come to scuff all of the rear body surfaces with red Scotch Brite and 150-grit paper to provide plenty of “tooth” for the hi-build primer to grip.  Now, it was time to start the slow process of masking every edge at the rear of the car to prepare for the application of two medium coats of PPG Shopline JP-205 polyester high build primer. 

I have come to love the convenience and time-and-material savings offered by the use of a professional masking machine for masking jobs like this.  A masking machine is simply a device that applies masking tape along the edge of a roll of masking paper and has a cutting edge along the bottom to allow the user to quickly tear off the desired amount of pre-taped masking paper.  All told, I reckon this device saves between 50 and 75% of the time that would be required to apply masking tape to the masking paper by hand.  Worth every penny!

Finally, the application of two generous coats of PPG Shopline JP-205 was upon us.  As primer products go, JP-205 might just be the closest thing to magic in a can there is!  Essentially, hi-build primer is a sprayable polyester body filler that is easily sanded.  By coating the entire panel in a thin, even coat of filler, the panel can be virtually perfected with every contour and body line capable of being as crisp and clean as the most perfect example anywhere.

Like regular body filling techniques, applying and sanding hi-build is an iterative process that relies on careful blocking with guide coat to ensure that every panel detail is perfected.  Once the body is essentially perfect, the hi-build is sealed with epoxy primer and the plans for base color and clear can be established.  Nope, this ain’t no “collision shop” operation here!

On what might end up being the last decent day of what remains of 2014 here in occupied Southeast Michigan, all of the subject panels were squirted with hi-build and allowed to dry for a few hours before the masking paper was removed.  The end result was a nice, contiguous base that will be ready for slow and meticulous block sanding to flatten every surface and them more and thinner applications of hi-build until the entire works is as close to perfect as I can manage.  However, in the meantime, we will let these surfaces cure for a few weeks while we begin to evaluate door hinge rebuilds, trunk hinge powder coating and some seam sealing.

Happy Fall everyone!

The die cast end caps on my 70 are actually pretty good examples.  But plenty of filling and sanding is still required to get them straight and smooth.  Evercoat Ever Gold glazing putty is my filler of choice for detail work like this.

 

Ted blocking out the end cap after a thin coat of glazing putty.

 

This shot really gives you an idea of how much work goes into getting all of the rear contours just right and how much variability there really is in the "factory" rear bodywork of these old cars.

 

The left side was actually a wee bit better overall than the right, but still requires a lot of work to get into shape.

 

With all of the detail filling work done and the contours smoothed up, the added character of the thin gap we added between the end cap and the quarter flange can really be seen.

One area that is often overlooked at the rear of 69-70 Mustangs is the outboard transition area between the lower rear window closeout and the rear quarters.  Most cars have a dip in this area as shown by the straight edge above.  A bit of filler is added to this low area on each side and carefully sanded to bring the surface level.

Here is the same area after filling and sanding.  No gap anywhere along the length of the straight edge.

 

Here is another look at the transition area without the straight edge in the way.  Very little filler is required to get these areas right.

To ensure the tight gaps we added to the rear quarter end caps are precise, I machine these custom spacers to the exact dimensions required to maintain the exact gaps every time the end cap is removed and re-installed.  Each spacer is number to match its individual stud as indicated by the numbers on each spacer and at the base of each stud.  Then, each spacer is epoxied to the base of each stud and installed on the car to dry permanently.

 

In this shot, you can see the spacers glued into place with industrial epoxy. 

 

The rear quarter flanges also require careful attention to ensure they are flat and square to match the end caps perfectly.

 

 

This shot shows how much work is often required to get the rear quarter flanges flat and straight for proper panel fit.

 

Using USC's Duraglas fiberglass reinforced filler, I even up the flanges on the back side of the rear valence to ensure the gaps are consistent when the panel is installed on the body.

Before masking, every panel gets a light scuffing to give the PPG Shopline JP-205 primer good "tooth" for adhesion.

Using a flexible sanding block with 150-grit paper, Ted carefully scuffs the inside radius areas of the quarters in preparation for priming with hi-build.

 

We start masking from the rear tail light panel forward in prep for the hi-build primer.

 

A professional masking machine makes masking large areas of a car amazingly quick!  We are ready to shoot some hi-build primer!

Starting with the smaller loose parts, everything gets two generous coats of JP-205 Polyester High-Build Primer.

Even with the slightly rough texture of hi-build primer, the deck lid still looks great!

And there it is!  The rear of the car is finally in its first round of hi-build primer and is ready to be blocked.  Lots of work yet to do back here, but this is looking pretty good!

Quarter End Cap & Rear Valence Work

Like all detail work, the process of creating subtle custom touches that don’t look like custom touches is extremely time consuming and tedious.  Such is the case when massaging the quarter end cap shapes and fits along with the rear valence corners.

The goal of the last few weeks has been to match the quarter end cap contours to the finished rear quarters to achieve a more blended and smooth look between the parts without changing the “stock” look of the body.  As simple as it sounds, the amount of work that goes into this deceivingly complex area of the car and the time involved in addressing these highly variable surfaces is very high.  As such, the photographs included in this update will not show dramatic differences in these areas, but rest assured, the up close and personal review reveals a significant improvement in look.  In fact, once the whole area is in primer, it will be very difficult to identify the true extent of these modifications, but the overall smoothness and refinement that will result will be a subconscious “home run”.  These are the kind of modifications that keep the knowledgeable admirer coming back to a car, time and again, to try to absorb all of the details they can’t immediately identify.  I love cars like that!

Following up where we last left off, the first detail that must be addressed is to carefully align the trunk lid and end caps to establish the most consistent panel gaps possible.  Once this is set, it’s time to machine aluminum shims that slip over each end cap mounting stud to allow the gaps to be precisely and repeatable duplicated each time the end cap is removed and reinstalled.  Due to the variability in the factory stampings and welded joints, each shim must be custom machined for each location to achieve the tight gap fit required.  Once each shim has been machined, it is indexed to its respective stud so the gaps assemble correctly every time.  From there, the shims are then carefully glued to the base of each stud with epoxy, making sure to avoid getting the epoxy adhesive in the threads.  The end cap is immediately installed on the body in the exact location that achieves the best fit, and then left overnight to dry completely.  With the shims permanently bonded to the end caps, it is easy to achieve the perfect gap time and time again during the fitting and smoothing process.

Next up, the painstaking work of filling an smoothing the end cap contours and lower valence corner transitions to precisely match the quarter panel contours begins.  The work begins from the “bottom up” as it goes and each valence corner is carefully massaged and filled until the transition from the quarter panel into the valence is smooth and the gap consistent on each side.  There really is not “magic” here other than to be very patient and sneak up on the final finish.  This is far more iterative than “collision shop” work and many thin layers of filler will be added and subsequently sanded away until the final shape is achieved.  Get used to this…….it’s part of the game!

Next, the primary attention shifts to the end cap fitting.  The end caps on the 69-70 Mustang are a die cast alloy and allow very little opportunity to reshape them with usual metal finishing techniques.  Fortunately, they are a pretty stable and solid work platform that allows very fine filling work to be done to correct their amazingly lumpy surfaces.

If you stare at the 69-70 Mustang Fastback body as long as I do, you start to pick up on exceedingly subtle idiosyncrasies that ultimately seem……..well……….out of place.  One such area is the way the factory end caps make the tail of the car look ever so slightly “pinched” at the rear such that the quarter-to-end cap fit seems rather ragged.  By spacing the end caps back a mere .050” or so, the contour transition becomes much more pleasing and allows them to be much more cleanly blended using relatively little filler.  After several thin applications of filler and very careful sanding, a final skim of finishing putty is applied to the entire repair to achieve a very smooth surface ready for high-build primer and final finish sanding before epoxy primer/sealer.  One clever trick that I use to keep the gaps tidy during the filling process is to use a razor knife to “cut” the gaps along the clean edge of the quarter and end cap when the filler is toward the end of the gel phase when you can safely shave the high spots with a Surform tool.  This allows me to add filler directly over the gap for ease of contouring.  On narrow gaps like these, you simply swipe filler directly over the gap, but on larger gaps, you must back up the gap with foam masking to prevent the joint from filling up and sagging.  Works for me!

The next phase of work involved preparing the front edge gap on the trunk lid for blending into the lower window panel and to clean up the upper transition quarter end cap edges and rear end cap faces.  This work involves very little filler and makes for a much improved appearance when finished.  You really wouldn’t believe how poor the surfaces on the rear faces of the end caps really are.  In addition, the front trunk lid edge rarely matches the lower window finish panel correctly and now is the time to smooth up this area as well.

So, with several days of work left in these areas, we will soon be moving toward getting the entire tail end of the car in a few coats of polyester high-build primer to allow the final finish work to be done.  This will include flattening the rear quarter flanges to provide a perfect mating surface to the quarter end cap flanges, finishing the outer flanges of the rear valence to present a clean, finished edge to the gaps, finishing up the front trunk lid edge fit, smoothing the rear wheel opening flanges, and scuffing the valence down to bare metal.  Plenty left to do in this area, and plenty left to report in our next update!

Right rear quadrant gaps are carefully aligned before any end cap contouring work can begin.  Gaps are set as close to 3/16" as possible and eah panel mounting location is indexed to allow precise positioning each time the panel or component is removed and reinstalled.

Left quadrant gaps are all set!  This area of the car is rather complex in that there are three (arguably four) critical gaps that must be managed at the same time.  Until each one is set to the exact width on each plane, no other work can be done to the end cap contours.  This is a careful balancing act that takes a lot of time to get right.

The gap at the leading edge of the trunk lid must be equal to the rest of the gaps to keep the refined look intact.  Before it's done, every gap edge in this entire assembly will be carefully massaged for proper fit.

Not to be forgotten, the end gaps on the lower valence receive the same attention as all of the others and the contours of these corners are carefully prepared to allow them to be smoothed with minimal filler.  This area of the 69-70 Mustang body is very often a very disappointing area on may cars due to lack of attention to gap detail.  Not here!

Right side valence gap is metal prepped and ready for a thin skim of filler to get the contour in shape.

The left side valence gap required very minimal work to get into shape.

The right side valence gap was a bit rougher stamping and required a little bit more filler work to get smoothed up.  This was somewhat more complicated based on the fact that the right side quarter stamping was a bit different than the left and required a bit more filler work as a result.

With carefully machined aluminum spacers in place to precisely establish the .050" gap between the rear quarter end cap and the quarter flange, the two components can now be carefully contoured to create a beautiful transition.  This area is another highly variable joint that often looks less than desirable on "stock" 69-70 Mustangs and I am not a fan of seeing this gap filled altogether.

Filler application over a small gap can often be accomplished without masking.  While the filler is in the gel phase, the gap can be cut with  razor knife on the "guide edges" to allow the gap to remain clean and easy to prep.

Left side end cap is now fully blended into the quarter contours and skimmed in glazing putty in preparation for high-build polyester primer application to perfect the surface.

Right side end cap contouring is complete!

With end cap gapping and smoothing complete, the focus can now be shifted to cleaning up the read faces of the end caps and smoothing the front trunk lid to body interface across the gap.

 

The remainder of gap smoothing on the trunk lid will involve very subtle applications of filler.  here, we have scuffed the primed surfaces on each side of the gap with 80 grit paper to give the filler a solid foundation. 

At the conclusion of this update, here's where we are:  The rear faces of the end caps are skimmed along with the front trunk lid edge area.  Several more hours of work are involved in these areas before we move to the application of high-build polyester primer and hand blocking every surface to the ultimate shape.

 

Trunk Lid Finish Work & the Beginnings of Quarter End Cap Gapping

It’s been a few weeks since our last update but things have been busy here in the shop and I am happy to report the trunk lid work is done and the results are superb.  Continuing the thread from our last update, the trunk lid required a bit of careful filler work to get it perfectly flat and ready for primer.  For the first round of filling, the work began with our old standby filler, Evercoat Rage Gold. 

Rage was applied in very thin, smooth layers and block sanded between each coat until any traces of imperfections were gone.  This is a very iterative and labor intensive job as the idea is to use as little filler as necessary to get the panel straight before moving on to high build polyester primer and fine finishing putty to get the  final shape perfected before applying epoxy primer/sealer.  This is the kind of work that requires plenty of patience, rock ‘n roll, and discipline with the sand paper to ensure you don’t gouge the surfaces and thereby create more work for yourself.  The key is to refresh the paper on the sanding blocks often and let the sandpaper do the work.  Don’t “muscle” it with the idea that you will get done quicker.  Ain’t gunna happen that way.

With the Rage filler taking care of the vast majority of surface correction, the time came to lock the surface down with a few thin coats of PPG DP40LF epoxy primer mixed as a sealer by adding about 15% reducer to the mix.  This would seal up the entire surface of the trunk lid and allow us to finally get a critical eye on the panel surfaces when all in a single color and with a consistent surface.  After a solid overnight drying period, we were rewarded with a very straight panel that was ready for the finer detail finishing that high-build poly primer and finishing putty would bring.

With the primed trunk lid surfaces thoroughly dried, the entire surface was treated to a rather aggressive scuff sanding to allow the PPG Shopline JP205 high-build polyester primer to grip the surface as aggressively as possible.  JP205 is essentially a “sprayable” and extremely high quality polyester body filler that is applied evenly over the entire surface of a panel and then very carefully block sanded to achieve a laser-straight surface.  This stuff might just be the closest thing to magic in a can that you will ever apply to a custom car body surface.  With a film build of only about 3 mils per coat, you can very efficiently apply a workable surface to the entire panel that is very easily sanded to virtual perfection in very short time.

In our case, we started with two moderate coats of JP205 and allowed this to cure overnight.  Then, the panel was carefully block sanded with the longest boards we had to carefully level the surfaces yet again.  With the darker DP40LF epoxy primer as a base, it was very evident that we had a few very, very subtle imperfections that we needed to address.  And this is where the high-build primer really shines.  By using lots of dry guide coat and 120 grit sand paper that was changed often, we were able to hone in on the specific areas that required more attention with extreme accuracy.

A second application of two coats of JP205 was all that was needed to completely eliminate the few remaining hiccups in the surface following a very deliberate and careful sanding exercise.  The final finish work was accomplished with a new product from Evercoat called Ever Gold finishing putty.  This is a brand new product in the shop and I have to say I absolutely LOVE this stuff.  It lays on exceptionally smooth and sands and feathers out to gorgeous finish.  This was used to correct the last tiny specks and pinholes that remained in the surface.

Finally, the “beauty” surface of the trunk lid was treated to two thin coats of PPG epoxy primer/sealer and allowed to dry for a few days before transitioning to the prep work required on the bottom side of the lid.

The only corrective work required on the bottom trunk lid surfaces was to tidy up the forward flange area that was welded up in the gapping process.  This was very easily addressed using the Evercoat Ever Gold finishing putty to smooth the grinding marks and create a flange that is virtually indistinguishable from a factory flange.  In fact, unless you followed the modifications here, you would never know the extent of work that had gone into this forward trunk flange.

Next, the entire bottom surface was scuff sanded in every nook and cranny in preparation for a few coats of PPG epoxy primer.  I really like using the 3M Scotchbrite “red” pads for a lot of this type of work as they are very flexible and durable and provide a great surface for primer without gouging up the metal in the process.  Then, the bottom surfaces were thoroughly cleaned and tacked off and two thin coats of PPG epoxy was applied to seal things up.  And with that, the trunk lid work was complete and the results look absolutely awesome!

Next up, we started the gapping process on the rear quarter end caps.  This is an area where I will divulge a little secret that can make a big difference in how a car is perceived at a show or cruise.  More on that in a minute.

Quarter end caps are a bit of a love/hate relationship on Mustangs.  In the case of the 69-70 body, these caps are die cast alloy and more often than not, do not match the exact contours of the quarter panels they are bolted to.  Complicating this is the fact that they can also damage fresh paint on the rear of the quarters if they are tightened down too hard and the factory gasket device is compressed.

Nine times out of ten, the end caps are hard against the rear quarter flanges when mounted to the body, leaving no “gap” at all.  I have always found this to look a tick bit odd when all of the panel edges around this part have…..well……gaps.  So, to remedy this perceived error (and here’s the secret), I carefully shim the end cap out away from the end of the quarter panel using simple hardware washers until I have a consistent and precise .047” - .050” gap across the entire flange.  This subtle modification creates many beneficial features.  To start, by creating this thin gap, the need for the rubber “seal” is completely eliminated and the potential to damage the paint as a function of securing the end cap is virtually eliminated.  Secondly, moving the end cap slightly rearward on the quarter allows more room to blend the end cap contours into the rear quarter for that extra detail that everyone notices, but rarely can put their finger on.  And finally, it allows the rear quarter flanges to be worked perfectly flat to match the end caps with precision and allows the end cap mating edges to be precisely fit to the quarter to give the quarter a cleaner, more flowing line all the way back.  The difference is rather striking for such a simple modification.

In our next update, we will be finalizing the end cap gaps and machining the final spacers that will be used to maintain these gaps with more durability and precision than the washer stacks will allow.  Then we will document the work going in to contouring these caps to perfectly match each quarter for that “super finished” look.  Also, we will start cleaning up the lower valence panel end contours and blending them into the lower quarter sections for perfect fit.  Lots more to come!

Several thin applications of Rage Gold filler leveled out the trunk lid very well.  The darker edges are actually the underlying base metal showing through the almost transparent feathered edges of the filler.  A good indicator of just how thin the filler actually is.

Sealed up in a few thin coats of PPG epoxy primer/sealer.

The PPG epoxy primer was left to cure for a few days and then scuff-sanded in preparation for a few coats of JP205 high build polyester primer.

PPG Shopline JP205 high-build polyester primer is essentially a sprayable body filler.  This stuff is rather nasty looking when applied but it blocks out beautifully and is a key in getting a panel laser straight.

Almost done blocking the first application of JP205.  This shot is very telling as it clearly shows the few bare metal high spots that were revealed that could not be felt with the hand, the darker grey slightly high spots where the epoxy primer was revealed and the light grey band about 10 inches up the deck lid that shows the guide coat in the area that requires a tick bit more work.  Lots of value in this shot for sure!

Another look after the first coat of JP205 was blocked down.  The back side of the trunk lid was surprisingly straight and required very little work to get dead flat.

I have been trying a new product from Evercoat called Ever Gold finishing putty and so far, I love the stuff!  This is an excellent fine filler that easily handles tiny imperfections like pinholes and sand scratches.  Sanding is a breeze and the finish is excellent.

These thin skims of Ever Gold were all that was needed to correct the sanding scratches and few pinholes we had .

Prep work for the second coat of JP205 high-build primer is complete and the panel is being tacked off before spraying.

The final coat of JP205 is on and allowed to cure overnight before final block sanding would begin.

Here is the trunk lid after final blocking on the JP205 high-build primer.  A bit of cleaning and tacking and we are off to epoxy primer/sealer!

All sealed up in PPG DP40LF epoxy primer/sealer wet out of the gun.  You can get a  idea of just how flat and beautiful the trunk lid is based on the reflection of the door frame in the surface.  Once this dries, we can tidy up the bottom surfaces and get them primed too.

In this shot, you can clearly see the silicon bronze weld bead along the edge where material was added to tighten up the gaps.  To ensure this modification would remain completely invisible, I decided to apply a thin skim of finishing putty along this edge to fill the grinding marks and any subtle dips that may remain after all of the work is completed.  The masking tape ensures I don't end up with a nasty edge along the back side of the flange when the filler is applied.

I went a little bit heavy on the finishing putty to give me plenty of material to work with when sanding this edge to shape.

With the welded edge smoothed up, I moved on to scuffing the rest of the surfaces to prep them for primer.

PPG epoxy primer fresh out of the gun looks fantastic, even on the bottom of the trunk lid where almost nobody will ever see.

Details are everywhere!  The modified flange looks like it came straight from the stamping press.

Quarter Panel End Cap Gapping Begins!

 

Rather than have the quarter panel end cap extensions mounted hard against the rear quarter flanges where they often damage the paint, I prefer the look of having a slight gap.  I start this work by shimming the end cap away from the flange using standard 1/4" flat washers.

I try to target a gap of .047" - .050" on the quarter extension/end caps for just the right look.

As soon as a gap is established between the end cap and the quarter flange, it becomes very evident how much work the quarter flanges will need to get truly flat along their edges.  It is amazing how much the quarter end caps hide when bolted up solid.

Where the gaps are a bit too wide (or narrow) I mark the amount they need to change directly on the part to allow me to correct it by the exact amount required.  In this case, I need to reduce the gap in this area by .020" to match the target gap.

Here is a section that will require slightly increasing the gap along a section about 3 inches long.

 

Once the end cap gaps are established, the look is surprisingly more refined.  A lot of builders like to mud these gaps closed, but that is a look I have never quite appreciated on the classic Mustang and is due, in most cases, to the obvious use of a lot of body filler to achieve the "seamless" look.  Nope.......not on this project.