Re: [Amc-list] Tankin' the 65 Project - Analysis

[Frank Swygert <farna@xxxxxxx>]

Great analysis! The urethane body panel adhesive would almost certainly NOT hold up under constant exposure to gasoline. I bet it would start leaking in a week or two if not days. I've had trouble with JB Weld holding, but that could be due to a narrow bead (intended only to seal) and the tank flexing a little (not positive if it does or not). Or maybe I didn't let it cure long enough before putting gas in. 

You don't have to braze a patch like that at all. Easiest leak-free way is to use screws or rivets then SOLDER the seams (and around the screws). Propane torch is hot enough. You just need at least 1/4" overlap. With 1/2" you could probably eliminate the screws. Solder will hold more than you think! The brazing method to use would be silver-solder. 

That's right -- technically it's actually a low temp braze rather than a high temp solder, but the common name is "silver-solder" for some reason. I forget what the temp break-point is between solder and brazing -- I think it's anything over 800° is brazing. Brazing uses a second (or third) metal to bond two pieces together, and can be used to bond dissimilar metals (which is why it could be the third metal) -- but requires over a certain temp to melt the bonding metal (lower temp is soldering). Of course the difference between soldering/brazing and welding is that welding actually melts the metals being joined, and some methods (TIG) don't even require a filler metal. The filler metal and the metals being joined must all have the same primary base, but can be different alloys. Stainless can be welded to plain steel, for example.

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Date: Sat, 29 Nov 2008 11:21:14 -0800 (PST)
From: Joe Fulton <piper_pa20@xxxxxxxxxxx>

Well, I have evaluated the options for repairing/replacing the gas tank in the 65 American. The entire rear bottom portion of the tank is rotten. 

Gas Tank Renu would cost $325 plus shipping both ways.  I estimate the total at about $400.  

Brazing on a big patch would work.  I have an oxy/acet rig but have never brazed.  I have ordered a free CD about the process but will use it for future reference.  I guess a cheap MAPP torch would work too.  There would be difficulties in getting a good fit for the patch though.  This would be done in conjunction with a fuel tank sealer kit.  Brazing rod and flux plus the sealing kit, plus any special tips for the torch etc. are estimated about $120, roughly.

I was tempted to use 3M body adhesive to adhere a plastic patch onto the bottom, but there would be questions about the compatibility of the plastics and adhesive with gasoline and the joints would be under constant head from any gasoline in the tank.  I can get sheets of HDPE plastic at work and could fit them exactly by heating and laying the plastic over the tank.   It wouldn't be like a patch on top of the tank.  This would be done in conjunction with a gas tank sealer kit though.  Cheap but "iffy". One tube of adhesive would run about $35 with tax plus the cost of the special squeeze gun $20 to $25 (estimate). I haven't priced them.  The plastic would be free.  The sealer kit would cost around $70 with shipping.  

The option I have chosen is to use a 1965 Mustang tank mounted endwise in the stock American tank location.  The dimensions of the tank almost match the American tank, but the filler port is on the incorrect side of the tank.  I can easily move the filler port but cutting and welding or brazing myself or can have it done at a local shop.  I have already ordered a Mustang fuel sender to replace the corroded American fuel level sender.  I'll order the replacement tank today.  Total cost for the tank should be about $160 including shipping.  Welding is estimated at another $20 to $30 if I hire it done.  I'll probably have to modify the fuel tank strap too, but that I hope can be done without costing me anything.

The tank would need to mounted endwise to keep the muffler in the standard position. It's a tradeoff between moving the filler port on the tank and exhaust work to reposition the muffler.  I'll make the final choice after I get the tank here at home.  The muffler might need to be replaced anyway but the tail pipe looks sound.  

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
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