Some old time listers may recall the rambling posts about my various
attempts at repairing my Cobra's gas tank a number of years ago. As it
happens, this story is still ongoing.
Before going on, here's a little background for those who weren't on the
list then or have forgotten. I'll start with a few words about the tank
itself: it has an elongated box shape with a sloping "roof" top. It's
constructed of terneplate, which is sheet steel plated with a tin/lead
alloy. Joined edges are crimped and soldered. A round filler neck is
soldered to the upper part of the rear panel and sticks up above the
tank top about half an inch. The neck lines up with a 2" diameter hole
in the bodywork above. A gas cap assembly screws into a threaded steel
ring which is connected to the filler neck by a short piece of rubber
hose. The tank is located just behind the cockpit.
About ten years ago the tank started leaking. I tried various in-place
repairs, but none really worked. I finally removed the tank and took it
to a radiator shop that "specialized in tank repairs", which pretty much
sealed its doom. I've already ranted about this on the list, so I won't
bore anyone with a repeat of this part of the story. Anyway, this lead
to a couple of more tank removals/repairs, including lining the inside
with a sealer. None of these repairs worked long term, so when I
embarked on some major car refurbishing a while back I decided to take
care of this problem once and for all. One possibility I briefly
considered was having the tank coated with Fiberglass, but in the end
decided the best solution was to replace the tank.
Since the supply of new and/or used tanks dried up more than two decades
ago, the only available option was to have one made. There were only
two outfits that I was aware of that offered custom fabricated tanks for
Cobras. One was Motorsports International near San Diego and the other
was a Cobra parts supplier on the east coast I'll only refer to as
Company B. MI's price was $1495; CB's price was $500. What to do? An
obvious no brainer, I figured. I ordered a tank from CB. If anyone is
interested in CB's name, I can supply it off list. In fairness, CB was
highly recommended to me by another Cobra owner who had purchased a
custom made tank from them.
The new tank had the same basic shape, of course, but was constructed of
heavy gauge welded sheet aluminum. Besides being new it had two other
advantages over the old tank: 1) lightness, and 2) supposedly better
seam integrity. But it was by no means perfect. The filler neck was
off center about 1/4" and too far forward by about the same amount. I
sent a longish e-mail to CB detailing this and a few other more minor
complaints. CB responded with the suggestion that I stick a piece of 2"
pipe in the filler neck and bend it to wherever it needed to go. I was
informed that this was their standard fitting procedure for these tanks.
The message seemed clear to me- CB didn't want to be bothered having the
tank returned for alterations. To be honest, I wasn't too enthused
about the idea either. Besides the hassle of boxing up such an awkward
piece, CB is located on the east coast and I'm located on the west
coast. What with shipping time back and forth, the time it would take
for the alternations, and perhaps more than one shipment/alteration, I
envisioned weeks going by before I had the tank installed. What I was
hoping for was an in-between solution like having me take the tank to
someone local for re-work or some suggested simple modification that
would improve the alignment. In a sense, I suppose I got the latter
solution, though I didn't find it very appealing. Aluminum is very
malleable and bends quite easily. What didn't appeal to me was putting
wrinkles in the rear of the tank around the filler neck since that part
of the tank is very visible from inside the trunk.
Rather than start right off with the pipe mod, I decided to do some
whacking in a few locations where the sun didn't shine- i.e., not
visible from inside the trunk. The filler neck was offset to the left,
so I did some minor bashing-in on the right side where the tank butted
up against the frame to allow a little more movement in that direction.
The filler neck faced forward slightly due to a distortion in the rear
panel which I suspect was caused by heat during welding. This
distortion allowed some flexing so I was able to tilt the neck back a
tad. Also the bend at the bottom rear edge of the tank was slightly
rounded so I "squared" it up with a few light hammer blows. All of
these steps taken together got the opening and neck to within about an
1/8" of being aligned.
Finally it was time for "the pipe mod"! With the tank still in place I
marked the location of the maximum gap between the filler neck and the
opening. I then removed the tank and stuck the pipe into the filler
neck. I had fitted a sleeve around the pipe for a snugger fit. A few
good tugs on the end of the pipe in the desired direction did pretty
much what I suspected it would do- elongate the hole rather than move
the neck. Oh well. Next I re-rounded the neck opening at the farthest
reach of oval with some ball-peen whacks.
Back in with the tank and sooo close! A little more nudging with a pry
bar. A few more taps on the front of the tank and finally just enough
clearance for the filler cap assembly go cleanly through the opening and
screw into the threaded ring. Out with the tank one last time (I
thought) to repaint the scuff marks on the frame I had made during the
multiple tank insertions and removals.
Perhaps not the most satisfying solution, but no worse than the roll-bar
clearance mod to the original tank. Because there wasn't quite enough
room for the roll-bar to clear the top-front of the tank, someone had
bashed that area in with a hammer. For years I thought this was
someone's clumsy DIY installation, but recently learned that this was
the "standard Cobra roll-bar tank modification". The new tank has a
wedge shape cut-out for the roll-bar, BTW.
I wished I could say that was where the story ended, but unhappily it
wasn't.
A few days after getting the car back on the road, I tried topping off
the tank only to discover that it leaked. Considering all the hassle I
had gone through to get the tank to fit in the first place, I was one
unhappy camper. I had specifically asked CB if the tank had been leak
tested before being shipping and was assured that it had been. No, the
leak had nothing to do with the munging I had done to get the tank to
fit- it was due to a flaw in one of the welds. There was a pin hole in
one of the welded seams well away from any of the areas I had banged on.
I e-mailed this complaint to Company B and received a response with an
apology, a vague reference to a suppler problem and an offer to send
some tank sealer. I felt this was a completely unacceptable response
and sent a message back saying so. I had gone through this nonsense in
spades with the old tank, which was the reason I had been willing to
spend that much money for a new tank. CB finally agreed to allow me to
have the tank repaired locally and bill them. In the interim, I had
sealed the leak with epoxy.
The final chapter?
Since I have gotten quite proficient at removing and installing this
tank, I got it out in record time last Saturday morning.
The first thing I did was pour in a couple of gallons of gas, seal all
of the openings, and then rotated it to every possible orientation so I
could check for additional leaks. I didn't find any, and since there
was still epoxy on the one known leak, there were no dribbles from there
either.
Not being very confident about finding anyone willing to weld a gas tank
that had once had gas in it, I made the assumption that I might be doing
the repair myself. For this reason I decided to clean the tank out as
thoroughly as I possibly could. I began with multiple vigorous sloshing
flushes, first with alcohol, then carb cleaner, and finally with a hot
TSP solution. This was followed with multiple hot and cold water
rinses. I was amazed at how much easier this was to do with a welded
aluminum tank than it had been with the original sheet metal tank
covered with pounds of solder. Another interesting thing was that even
though I could no longer smell gas inside the tank, there was still a
noticeable carb cleaner odor even after many follow up washes and
rinses.
Next I removed the epoxy patch and resealed the tank. I had kludged up
a tire valve fitting in one of the outlet holes so was able to pump air
into the tank with a bicycle pump and check all of the seams with soapy
water for leaks. I found no leaks, including the area where the epoxy
patch had been, even though the hole in the weld was clearly visible.
I'm guessing I didn't get all of the epoxy out of this tiny pin hole
opening.
My plan, assuming I couldn't find anyone to fix the weld for me, was to
patch the hole with alumibraze using either a propane or a MAPP torch.
I figured I could fill the tank with water and/or CO2. Do hobby shops
still sell those little CO2 cartridges? I haven't seen one in years.
As it turned out this plan was unnecessary because I managed to talk
AMAC Fabrication, a local race car fab-bing shop, into doing the weld
repair for me. I'll be picking the tank up later in the week. And yes,
I did inform them that the tank once had gas in it.
Roland
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