Replacing the Roof Skin – Part 1

Easter weekend and I have an extra day to spend in the shop and what better excuse would I need to start the removal of the rusted and damaged original roof skin on the Boss than that?  But first, a little background…..

Having committed to replace the roof skin some months ago, I wanted to make sure, in every practical way, that the original fit and finish of the window openings and body contours would be as perfect as they could be.  As such, I decided to make simple templates to allow matching the window openings and to have a place where exact measurements could be made to verify the fit of the new roof during installation.  So, the first order of business was to make these templates and measure everything before any of the roof skin removal work began.  Ted and I had a pretty solid plan laid out for the proper templates and we set about making them in an evening using the scrap cardboard I had left over from the shipping box the new roof skin arrived in.

With the templates made, I began marking the exact cut lines I would follow along the edges of the original roof to allow me to remove the bulk of the damaged skin in a single piece to allow work on the welded flanges to be much easier.  Using my trusty paint markers, I traces the entire perimeter of the roof about 1.5” inboard of the seams and flanges.  Then, with a box of fresh cutoff wheels in the queue, I very carefully cut along my painted cut lines, making sure to only allow the blade to penetrate the skin just enough to cut without damaging the under-structure beneath it.  This slow progression was particularly taxing on the cutoff disk life and it took about four fresh cutoff wheels to complete the job.  But, after less than an hour of work, the major portion of the roof skin was cut away and work would then shift to the careful removal of the perimeter flanges.

I wanted to preserve as much of the front and rear window opening flanges as I could to allow me to compare them to the contours and features of the new roof skin.  Since these were rather straight forward spot-welded sections, it didn’t take long to cut the spot welds free using my Blair spot weld cutter tool.  As each window flange was cut free and some small burs removed, I compared each one to the new roof skin to see how things were shaping up in these areas of concern.  What I discovered was an absolute stunning fit which quickly offered a welcome measure of comfort that the rest of the new panel would be workable as well.

With the front and rear window flanges removed, I could now start evaluating the condition of the underlying structures of the roof to see what, if any, additional repairs would be necessary before the new roof could be installed.  To my utter amazement, the structures were in fantastic shape with only the 40-year-old surface rust that is expected on surfaces that never received any form of protective coating during manufacture.  In fact, once the cobwebs and mouse turds were brushed free, the metal was nearly perfect in all respects.  This was good news I really needed and provided great confirmation that I had made the right decision to replace the original roof with new metal rather than risk a repair to the original.

At this point, the drip rails were all that remained to remove and I knew in advance these would provide a challenge in that there were an extraordinary number of spot welds along each rail (about 45 on each side), and the welds were smaller and more closely spaced than what is normal around the rest of the car.  This pretty well eliminated the possibility of using a conventional spot weld cutter in this area as there just wasn’t the room necessary to fit the tool in the confined space.

The solution to this problem was to revert back to my trust cutoff wheel to very carefully grind through the spot welds just enough to allow them to be popped loose with gentle prying/peeling on the loose end of the scrap roof skin.  On first blush, this sounds like a horribly barbaric means to address spot welds (Ted thought I was positively off my perch), but as long as each weld is clearly marked before you start, and a very careful and light hand is used on the cutoff tool, you will be amazed at how quick and effective this method of spot weld removal can be with absolutely minimal impact on the thin, underlying base material.  In fact, once I got going, each drip rail required less than 15 minutes each to remove and that included cleaning up any burs left behind.  Sometimes you have to see it to believe it, but the technique works and works extremely well.

Now that the old roof skin was completely out of the way, I spent a few minutes grinding down the remaining spot weld nubs around each window opening and across the top of each quarter panel seam.  Then, it was time to test fit the new roof skin to see where we were in the grand scheme of things.

Much to our amazement, the new roof skin almost dropped right into place with nearly every flange settling nicely and cleanly.  We clamped the panel around the flanges and started assessing the fit more critically and found that only small tweaks would be required to get the roof to fit almost perfectly.  The critical contours appear to be spot-on and after some small tweaks to get the roof shifted toward the driver side by about 1/8”, we should be in excellent shape when the time comes to lock it down for good.  To say I am stunned at this stroke of fortune would be an understatement!

Now comes the tedious task of addressing the surface rust on the inner roof structures and getting everything prepared for welding.  Every flange will require exceptionally tight fit to be properly and cleanly welded into place with maximum effect and best appearance and many hours of prep work will be required to get there.  So, the next few weeks work has been defined and we are off and running in that direction.  Part 2 is on the way!

To ensure the fit of the new roof skin would match the original as much as possible, patterns were made to match the front and rear window openings and to allow exact measurements to be taken at precise locations around the opening so fit could be verified.

 

A single pattern was made for the front window opening that could be simply flipped over to verify the other side.  Measurements were written directly on the pattern for reference later on.

Here is the front window patter flipped to the passenger side for fit.

The hole in the middle of that yellow circle is what started the entire roof replacement discussion (more later).  More importantly, you can clearly see the yellow cut line I marked with my paint pen and the clean cut created by the cutoff wheel.

This is the cut line around the rear window opening.

 

Here is the cut line around the top of the front window opening.

I kept the cutting depth rather shallow to avoid damage to the underlying roof structure.

I was expecting a disaster under the roof skin once it was removed, but to my amazement, the roof support structure was in excellent shape with only surface rust to be seen.

This is the spot that changed everything.  After breezing over this rust spot with a wire brush several months ago and immediately breaking through, I though the world was truly against me.  Since it was located above a structural beam and I couldn't see it from behind, I feared the worst was being hidden from view.

This is the same spot from underneath.  What it shows is the pit was exclusive to the outside surface and not disguising a disaster on the inside.  Though this photo makes the interior surface look worse than it is, careful inspection shows a lot of clean metal, a fair amount of red oxide primer over spray and a smattering of surface rust.  As odd as it sounds this was a fantastic discovery.

Again, worse in pictures than in person, the inner roof structural beams were in excellent shape with only surface rust to contend with.

Even in the rear quarter to roof flange area, the condition of the metal was excellent.

 

This little bump in the middle of the rear roof brace is actually an alignment aid used to get the roof skin properly positioned during production.  It will serve the same function when the time comes to fit the new roof skin.

We were careful to remove the front and rear window flanges intact so they could be used to verify the contours and fit of the new roof skin in this area.  They will also function as patterns to position the trim rivets when the time comes.

The Blair spot weld cutter does an excellent job cutting spot welds on a job like this.

By comparing the original window flanges directly to the new roof skin, we were able to verify the new roof skin would work very well for our needs.  Quite a comfort seeing such good fit on panels separated in manufacturing date and tooling by some 43 years!

The front upper windshield beam is in excellent shape as well.

Upper windshield corner looks great!

Diver side quarter panel upper seam doesn't get much better.

Using a unique spot weld cutting technique, the drip rail roof sections were removed quite quickly and with virtually no damage to the base material.  Cool trick!

With all of the spot weld nubs ground smooth, the new roof skin dropped on with amazingly good fit.

With only the window flanges clamped, even the quarter panel flange fit is superb.  A couple of strategically placed Clecos and we will be in business.

Beautiful front driver side window opening fit!

Passenger side front window fit is also excellent!

Exterior Floor Final Priming & More Roof Skin Adventures

Since our last update, I am happy to report things have moved along quite nicely on several fronts.

With our seam sealing (mis)adventures long behind us now, the focus was to get the exterior floor prepared for final priming in PPG DP90LF black primer.  After a few conversations with the nice folks at U-POL regarding the best platform to apply Raptor Liner, I was encouraged by the fact that a good epoxy primer like DP was lauded as an excellent base for the Raptor.  With that in mind, I purchased a quart of the DP90LF and we set about masking and priming the floor over the course of about two solid evenings.

As I have mentioned before, the PPG DPLF primer is just about the best thing since pants with pockets when it comes to primers.  After shooting the DP90LF, I have another “like” to add to the growing list and that relates to the very nice matte finish the DP90LF exhibits once it dries.  In fact, I like the finish so much, that if I were to look for a matte black top coat for just about anything under the car, I’d just have a single stage urethane mixed up to match the DP90LF exactly and never look back.

Anyway, after a few hours of careful spraying, the floor was completely primed and the smooth, molded look we were after was quite handsomely satisfied.  The lower floor looks absolutely fantastic if I say so myself.  So much so, that I am quite confident the application of the Raptor spray bed liner material will achieve the exact finish I am looking for and will make for a very pleasing look that will be extremely durable.  But for now, we will purposefully shift the focus to the roof skin adventure in order to give the DP plenty of time to dry to full hardness (and the weather to warm up a good bit more), before we venture off to spray the Raptor and finish up the lower floor.

And that brings us to the latest chapter of the roof skin chronicles.  When I last left off, I was grappling with the decision to wait an additional 4-6 weeks for the roof skin I had ordered through NPD to arrive after making its enviable California-to-Florida southern tour of the United States before making the trek to the Michigan NPD warehouse where it would then be mine.  I guess I just couldn’t accept that as the way things had to be, so the day after receiving this news, I decided to go on a mission to see what alternatives there were to sourcing a new roof skin sooner than later.  And a good effort it was indeed!  Very quickly, I was able to find a very tidy deal on a new roof skin from another of my favorite Mustang parts suppliers:  Tony D. Branda Performance in Altoona, PA.  Of course, the “elephant in the room” was whether or not they actually had a roof skin in stock and if the shipping costs were going to torpedo the deal altogether.  So I made a quick call to them, and as I have come to expect, got a very knowledgeable gentlemen on the phone who went out to the warehouse and physically put his hands on the part to make sure it was what it should be.  When he came back to the phone a minute or two later with the good news, the shipping costs were estimated, and the deal was struck.  The trucking company would deliver the roof to my employer’s shipping dock and I would get a call when it arrived. This was Wednesday morning, March 20^th about 10:00am. 

Friday, March 22^nd, about noon I get a call from our shop manager with “your roof just arrived.”  Wha?  At this point the native Texan in me came to the fore and “Yer sh*ttin me” was all I could muster.  In less than 72 hours from the time I placed the order with Branda, my brand new Dynacorn roof was in my possession and ready to become integrated into my excruciatingly long and complex project.  THAT, my friends, is called SERVICE with a capital “S”!  And to top it all off, by the time the dust had settled, after my 10% off St. Paddy’s Day discount had been applied, the entire adventure only cost me an extra $37.60 more than my previous order.  I am lovin’ this.

Fast forward a day, and dad and I very carefully unpack the roof and inspect it from stem to stern.  Having had mixed results from Dynacorn panels in the past, I am naturally skeptical at what I will find.  The good news is the panel appeared, by all intents and purposes, to be nearly flawless!  For me, it’s hard to imagine such a large and delicate panel making such long trips without a hint of damage, but this one did and I am duly impressed.  A quick call to NPD to cancel the original order and the dilemma of the roof skin was solidly closed.

And so, the course of the next few weeks has been set, and the process of removing the old, damaged roof skin will begin in earnest.  I am desperately keeping my fingers crossed that what I find underneath the old skin is sound and without major repair requirements.  With renewed energy and a solid plan, I am on it!

With the 3M sealer dried, the entire lower floor was lightly scuffed (again) to provide a good bonding surface for the PPG DP90LF black epoxy primer.

Taping off the floor was comparatively easy since we wanted everything from rocker to rocker and firewall to tail light panel completely primed.

We purposely avoided priming the rear fender lips as they will require additional work before they can be finish-primed and the fact that they will be body color when completed anyway.

Good 'ol Ted "takin' care of biznezz"......masking off the rockers.

More masking around each fender opening.

Here, the firewall has been masked all the way back to the joint where the floor pan meets.  This is an excellent and convenient place to mask as it allows the floor to be treated differently than the firewall.  This allows the engine bay and firewall to be a different color than the lower floor without being visible from the top.  A very clean transition.

The trunk floor is masked from the inside to allow the edges to be "soft" in the way they feather into the interior.  Eventually, the trunk area will be sprayed with DP90LF primer as well.

Starting to cut-in the floor joints.  I ended up shooting the entire floor with my small 3oz 3M PPS cup as it was much easier to maneuver in the tighter spaces of the floor.  This used up quite a few disposable cups, and required several mixing cycles, but it proved to be the best way to go overall.

 

Cutting in the front part of the floor around the cross member and subframe connectors.

I sprayed the floor in "halves" to allow complete access to the intricate areas around the floor.

After rolling the car over to the other side, I sprayed the other half.

Another round on each side to touch up any light spots we could find and we were done!

I love the finish of the DP90LF.  This is an excellent chassis black color and I would not hesitate to match paint to this color and finish for final chassis painting if needs be.

You can start seeing how much smoother the seams look in this shot, especially with everything is a nice uniform black.

Trunk floor area also looks very clean and smooth.

"Yer sh*ttin me!"  A new roof skin!

Exterior Floor Seam Sealing Completed, Roof Panel Mysteries and a Moment of Silence for a Trusty Tool

Starting from ground zero can be a bit disheartening on so many levels, but for once, I was very happy to be starting from this distinguished point with a clear understanding of what NOT to do.

Recalling the last installment, our first attempt at seam sealing the exterior floor of the car went…..well…..badly.  The good news is, we learned a lot in a very short period of time and were able to get ourselves back on plane to start over with new confidence. And that’s exactly what we did!

As before, the exterior seams were carefully taped off to allow nice clean beads of seam sealer to be laid down, smoothed and allowed to tack a bit before the tape is removed and the sealer is left to dry.  This technique is fairly exclusive to the “custom” side of the hobby as the purists often get purposefully sloppy with seam sealer to duplicate the rough patterns and textures applied by the factory.  However, by taping and smoothing as described here, the seam is very smooth and slick, and when top coated with epoxy primer and later, sprayable bed liner material, the panels take on a very smooth, almost molded appearance that I find very attractive.  It’s quite tidy in fact, and that after all, is what we’re after!

In any case, the 3M Urethane seam sealer worked extremely well and by using xylol (xylene) as our solvent, it remained quite happy and dried to a very nice finish.  A little trick I learned is to carefully read the ingredients of the sealer for clues on what type of solvent will generally work.  In this case, xylol was part of the ingredients of the sealer and worked perfectly.

Urethane sealer is pretty interesting stuff in that straight out of the tube; it dries to a paintable finish in under an hour above about 60 degrees F and 50% humidity.  However, when you endeavor to use a solvent to smooth the finish as we did here, it is best to allow a few days before paint to allow all of the extra solvent to flash off completely.

In any case, Ted and I were able to knock out the entire job in a few nights and our focus will not turn to preparing the lower floor for a couple of coats of DP90LF (black) primer and later the U-POL Raptor urethane bed liner material.

In other news, I have struggled with what to do with the rather sketchy condition of the roof panel on the car for several months.  I have purposely left this decision until last to give myself adequate “think” time to try to make the best decision possible for the car and ultimately, I have decided the roof needs to go.  I really tried to avoid this particular bit of work for many, many reasons, but the old girl deserves the absolute best and that’s what she’s gunna get.  Anything less at this point in the project is simply false economy.

With that decision firmly established, I trotted down to the local NPD warehouse to lay down the bones for a brand new roof panel.  However, fate would decree differently.  The nice gentleman behind the counter rounded in his chair after typing in my rather significant order and informed me that the roof panels were “temporarily discontinued”.  I was mortified.  After struggling with the decision for so long and avoiding the weighty time penalty it would impose, I was now being told I was too late.

But wait!  There’s more.  Mr. Counterman allowed that there was one in the California NPD warehouse, and if I wanted it, he could ship it out to the Michigan location at no charge.  At this point, I asked him to please call them and ensure that it was indeed there and if so, I would take it and pay for it in advance.  They did, I did, and the deal was struck.  In “about two weeks”, a new roof panel would be in my possession and the last major panel replacement work could begin.

Fast forward two days.  The phone rings and it’s Mr. Counterman looking for yours truly.  Apparently, my spendy new roof panel will now take 4 to 6 weeks to arrive and in the process, it will have to make a coast-to-coast tour from California to Florida and THEN make its way to Michigan.  Ya……..that makes perfect sense.

Anyway, Mr. Counterman asks if I still want the panel or if I want a refund.  After a moment of reflection, I decide to leave the order standing, but have now committed to trying to find another panel somewhere else without having to wait……even if I have to pay the shipping charges to get it.  Can’t anything be easy?

And finally, a moment of silence for a trusty old tool that has finally met its end.  My nearly indestructible Kodak digital camera has snapped its last images for this project and I feel a bit of personal loss at its demise.  To date, this camera has contributed every image shared on this blog and thousands more beyond that.  For the price, this camera was a far better tool for taking pictures than most of the similar devices I have experienced and I found myself resorting to it more often than not when I needed something that simply worked.  Adios amigo…..

Taping off the seams once again for round 2 of under body seam sealing fun!

Ted is an excellent hand at taping "his" end of the car.  He manages to stay just out of arm's reach, forcing me to endure MANY off-handed comments and copious whining.

After a few hours, we have one side taped off and we are ready to give the seam sealer another shot.

Success!  The sealer went on quite smoothly and the xylol solvent worked very well at feathering the edges.

After a few solid hours of carefully orchestrated teamwork, Ted and I had caught ourselves up to where we had previously discovered our earlier error.  After an overnight cure, the sealer was nice and firmly cured and we could move on to the other side.

With each seam taped off, we run about a 12-18 inch bead of sealer and then smooth that section with xylol before moving on.  Ted uses a butter bowl to hold a small amount of xylol to make it easier to chase the seams.

At long last, the other side is now sealed and we can move on to the harder-to-reach areas at the rear valence to finish things up.

Ignore the date on the picture!  Camera operator lacked sufficient talent to get that part of the new digital camera set up properly.  The good news is the rear wheel tubs are sealed and look very nice and ready for finish.

The rear axle tunnel area is one of the more complex areas to seal, but looks very clean when the job is complete.

Here, Ted has started scuffing the floor in preparation for the final coat of primer.

Synthetic scuff pads are great for scuffing the surface of the primer to get it ready for it's final coat.

And there it is.  The floor is now completely sealed and scuffed and we can now begin preparations to get the floor in a nice fresh coat of PPG DP90LF (black) primer.

Exterior Floor Seam Sealing Take 1: One for the Blooper Reel

Have you ever walked in your freshly mowed grass barefoot, savoring ever cool, comfortable step, only to rudely discover your favorite family pet or neighborhood menace has left you a warm, creamy surprise that is now gently squeezing between your toes?  ALL of your toes????  Yep, that’s where I’m at……..including the smell.

Fact is……I blew it.  I blew it and it’s my own fault for the mess I’m in and now I am pondering what to do to get myself back on the porch and close enough to the water hose to rid myself of this embellishment so I can feel “clean” about my state of affairs again.  And right about now, the “porch” is way the hell over there!

When we last left off, the interior floor had been completely seam sealed and the comfort level with the 3M urethane sealer was high.  With momentum on our side, we drove straight into seam sealing the exterior floor with enthusiasm.  We began by carefully taping each side of the seams on ½ of the exterior floor to begin applying the 3M urethane seam sealer and smoothing the edges as planned.  Only this time, I would be using the grey version of the sealer (3M Part # 08361) as it would more closely match the primer color and I happened to fall into a good deal I couldn’t pass up on 4 fresh tubes of the stuff.

In theory, this should have been a cake-walk job as all we needed to do was follow the same techniques we used on the interior floor and we would be golden.  In fact, everything about the “technique” side worked exactly as planned………with one tiny little exception.  For some unknown reason, I had a mental misfire and decided to use old fashioned big-box store lacquer thinner as the solvent to smooth the seams as we put them down.  After all, I had a fresh gallon of the stuff handy and I quickly discovered it worked phenomenally well in smoothing the seams to a glass-smooth finish……..and that’s where the wheels fell off the wagon.

I’m telling ya…..we were making smoke!  This stuff was laying down smoooooth and we were moving through the project like poop through a goose.  As we approached having the first half done, it was time for the requisite potty break, so in the house I went for a slight pause in the used beer department (ok, used coffee ‘cuz I HATE beer, but you get the idea).  On my return, I decided to check the first few sealed areas to see how things were coming along.  I might have mentioned this stuff cures rather quickly……..most times……..if you do everything right…….and you give it a little time…….it USUALLY cures quickly.

Well, my discovery was of the warm, squishy variety mentioned in the first paragraph.  Not only was the sealer just as sticky and creamy as the moment I put it on, it still smelled like it came fresh out of the tube.  SH*T!  What the…..

Immediately, all manner of progress came to a screeching halt, my restoration “man-card” was on the brink of revocation and the entire operation was packed up for the night.  I decided the best position to adopt was to stop where I was and see what happened after a solid 24hr drying period.  Normally, this would be plenty of time to have the sealer cure quite nicely.

24 hours came and went.  Then 36. Then 48 hours passed until I had the courage to go back out into the shop and see what had transpired.  With severe anxiety, I extended my stubby digit into the thickest section of sealer and………..damn near pulled back a stump!  SH*T! SH*T! SH*T!  My greatest fears were immediately realized in one simple motion.  Like a fresh, industrial-strength rubber booger, the sealer was just as raw and fluid as the moment I put it on.  Not a hint of curing anywhere, on any seam.  And then……..depression set in.

What now?  How do you get uncured urethane sealer out of the seams with any hope of having them clean enough to reseal later on?  Moreover, why the hell didn’t it cure!?

And then, like a punch in the gut, it started to come to me.  I changed something in the system.  I changed something out of convenience and it bit me in the butt.  The lacquer thinner!  That was the ONE thing I changed and that HAD to be the culprit!  But WHY?

So the research and noodling began.  What about the lacquer thinner trashed the party and how was I going to correct this error so we could get back on track?  So…..I started with basics:  read the product info for the sealer.  Blah, blah, blah……tools easily……moisture curing…….use no solvents containing alcohol……stops the curing process…….wha?  Come again?  Stops the curing process?  Alcohol huh?  But I used lacquer thinner and that……….(read the ENGLISH side of the can)…….HAS ALCOHOL IN IT!  Methanol to be exact.  Suddenly, my love affair with this awesome form of racing fuel has become tarnished forever!  The entire operation was undone by the very thing 3M tells you to avoid – alcohol.

So now I knew the cause of my dilemma, but what of the solution?  More noodling.  Days of it in fact before I reasoned through the solution (and monitored the state of the urethane sealant over time).  After a week, the goo was still goo, so I started digging at the thicker sections to see how hard it would be to scrape out.  What I discovered was an unexpected and welcome surprise.  Beneath the uncured surface of the urethane was nicely cured sealer!  Almost immediately, I realized the substance that was at the root of my grief was now going to deliver me from this evil if I was patient and careful.  So, it was time for a test!

Using a cheap paint brush I cut down to make the bristles short and stiff, I poured some fresh lacquer thinner in a bowl and proceeded to scrub the crap out of a one-foot long section of uncured urethane sealer to see what would happen.  To my utter amazement, the uncured sealer washed cleanly away leaving only the cured urethane behind, which as luck would have it, is quite impervious to the lacquer thinner when fully cured.  That’s it!  After an overnight drying stint, I came back the next day with my fingers crossed and discovered that the cleaned section was free of uncured sealer and although I would have to scuff and re-prime the areas to cover the small areas of exposed bare metal, I had a solution to the problem that worked!

Essentially, what I had discovered was that only the sealer that had come into direct contact with the thinner was prevented from curing.  But, the sealer deep into the seams and crevices that did not come into contact with the thinner cured normally by simple exposure to the moisture in the ambient air.  How lucky can you get?

So, with a solution developed, Ted and I set about three tedious days of scrubbing every last hint of uncured urethane seam sealer out of every seam we applied it to using our bobbed paint brushes and lots of lacquer thinner and paper towels.  It was messy, nasty and sticky work, but in the end, what we were left with was cleaned seams (again) and many areas that required fresh scuffing and primer to get back to level on the dial and start back in a positive direction.

With our clean-up work complete, we prepped and primed the suspect areas with two coats of DP40LF primer and let everything cure for a few days before sizing things up for our next seam sealing adventure………without all the drama.  I promised I’d show the good and the bad in this build and there ya go!  I sure hope this helps someone avoid making the same mistake I made!

What a beautiful place to start a seam sealing job, eh?  Nicely scuffed and cleaned exterior floor.

Taping the seams is a technique that allows me to geth the finish on the seam sealer that I want.  After applying the sealer, we peel the tape off and smooth over the sealer once again for a nice clean look.

And here is where things went off the rails!  Though those seams look nice and smooth, the sealer would not cure because I sued lacquer thinner as the solvent and the methanol contained in it stopped the urethane curing process DEAD!

Yep.  Thant pretty much sums it up.

After three days of scrubbing the uncured seam sealer off the car, what was left was thin traces of the cured sealer and a lot scuffing required to get the surfaces ready for primer.

Here, the thin (almost white) traces of seamk sealer are all that is left after the serious scrubbing they got to remove the uncured sealer.  What was left behind was solid, fully cured sealer.  Yay!

Here Ted is swabbing everything down with wax and grease remover in preparation for re-priming the seams we had to clean up.

Here is the floor after two medium coats of DP40LF primer.  The shinier traces around the lower seams is the fresh primer.  Thanksfully, we had only done about 1/3 of the lower floor pan before the wheels fell off the wagon.

Re-primed axle tunnel area.

Re-primed trans cross brace and shifter area.

 

Fitting a Stainless Fuel Tank & Interior Floor Seam Sealing

We are ROLLING and it feels good!  With the interior primed and scuffed we had reached the point that a brandy-new fuel tank was needed to finish up the fitting requirements before the interior panel seams could be sealed in preparation for finishing.

In the interest of longevity and fuel system integrity, I had long ago decided I would fit a stainless steel fuel tank in my car.  The availability of stainless tanks is unfortunately not very good, particularly if the goal is to have something that looks like a production tank when bolted in place.  Fortunately, I was able to find a very nice polished stainless tank through recommendations on several Mustang forums.  In less than a week, I had the new tank sitting in the shop and began fitting the tank to the car.

One major change I made right off the bat was to drill out the self-tapping screw holes to allow conventional bolt-and-nut fasteners to be used to secure the tank.  Why?  Because I like it this way and the fastener choices are much more pleasing to the eye when finished.  Also, I positively hate sharp pointy things lurking under a car that never seem to spare an opportunity to bite you when you least expect it and the self-tapping screws are excellent in this capacity.  Out they go…..

As expected, I had to do a small bit of trimming of the outer tank mounting flange to eliminate the hard edge interference on one corner.  This was a very minor detail that was quickly remedied with a cutoff wheel and some quick file work.  However, once this was done, the tank fit the opening perfectly and I was able to mark and drill the final three mounting holes in the forward trunk floor lip, and after a quick pass with the deburring tool, I was mixing up a small batch of primer and spotting over the fresh holes in preparation for the seam sealing work to come.

For me, seam sealing choices represent a real struggle.  Some require bare metal, some require primed/painted metal, some are solvent cured, some are moisture cured, some are clay based, some are polymer based, etc., etc.  At the end of the day, I have firmly decided I don’t like seam sealers designed to be applied over bare metal.  Too many opportunities to trap evil things and with the experiences with the factory seam sealers and the piles of rust under them I discovered, I will not duplicate that condition again if I can help it.

At the end of the day, and following many, many hours of research, I settled on the 3M Ultrapro Urethane seams sealers designed to be applied over primed/painted surfaces.  By definition, this type of urethane sealer is “moisture cured”, which means it uses atmospheric moisture to start the curing process.  That, of course, is the reason that this type of sealer should never be applied over bare metal as it will simply accelerate the rusting process as a function of the curing process.  However, since I had all surfaces solidly primed with PPG epoxy and my ultimate faith in the PPG product is quite solid, I liked this option best of all of those I examined.

For the interior, I decided on the 3M #08363 black urethane seam sealer as it would be essentially unseen in finished form and will be painted in flat black urethane paint as a final interior finish before carpet and upholstery installation.  This product is a moisture-cured urethane and can be rather easily tooled with water, or most thinning solvents like paint thinner, wax & grease remover or Xylol (xylene).  It’s worth noting that the interior was a perfect place to experiment with smoothing techniques since I wanted to make sure we had the technique down before moving on to the “cosmetic” seams on the exterior floor later on.

The application gun used for these sealing products is not your run-of-the-mill caulking gun, although they look for all intents and purposes the same.  Specifically, the gun required to apply the heavy-bodied sealers has a higher leverage ratio by about twice over the home improvement variety caulking guns.  Generally speaking, you are looking for a leverage ratio of about 26:1 minimum to push seam sealers without killing yourself.

With all of the prep work in place, the time was right and conditions perfect for Ted and me to set off sealing ½ of the interior seams on one evening and finish up the balance on a following evening.  This is very slow work as you can only apply about 12-18 inches of sealant at a time max before you must shift to smoothing or it starts getting pretty gummy.  This time amount gets proportionally shorter as the humidity goes up as this directly accelerates the cure time and therefore leaves less time for tooling the seam.  In any case, making this a two-person job is the most efficient way to get the job done with relative ease and consistent results.  It’s messy work and you end up contorted into rather unflattering positions, but having extra hands and eyes on the job makes for a much less tedious experience.

After about three tubes of sealant and two solid evenings of effort, the interior seam sealing was complete and we could allow a few days of cure time to evaluate the job.  Fortunately, the finished product looked very nice and the cured material was staggeringly durable and well cured.  I like this stuff.

With confidence in the 3M sealer high and a comfort level in the application technique and smoothing, we began preparing the exterior floor for the same treatment.  This is a bit larger job as there are several more seams that require careful smoothing.  This will involve masking almost every seam and smoothing and pulling the masking as we go.  This makes for very tedious work, but also ensures the best quality finish and the smoothness I am looking for.  At the end of the day, I want the seams under the car to appear smooth and molded after the application of the bed liner material.  We will tackle that work in our next update!

Here's Ted looking over the fuel tank mounting area.  Gotta fill it!

Where the alignment drift is seen through the mounting hole was once the location of a self-tapping screw hole.  I don't like these punched holes and the jagged and unfinished look they have so each one was drilled out and smoothed to allow standard bolts to be used for tank mounting.

The buff stainless tank looks very tidy under the Boss.  Also note the convenient fuel drain on the right front corner of the tank.

Only slight flange trimming was required to get the tank to fit perfectly.  Here is a shot of the nicely polished top from the interior of the car.

Another shot of the polished stainless fuel tank top from the rear trunk lid opening.  Too bad no one will ever see it!

And the trick shot of the day!  Here is a look at the INSIDE of the stainless fuel tank.  just as nice on the inside as the outside.  Lovin that.....

 

Here's Ted again showing his well-honed skills at smoothing the 3M urethane seam sealer with a bit of Xylol.

 

Right front interior panels all sealed up!

Right rear interior panels seam sealed and drying.

We tried a few different techniques for smoothing the seam sealer and settled on one that requires masking, smoothing, de-masking, and smoothing one last time.

Left rear view of the sealed interior and trunk area.