New or repaired fuel tanks for 308?

So I decided to cosmetically freshen my fuel tanks during my engine bay makeover, and pressure washed the textured coating off before doing a thorough clean to prepare for new coating. There were some visible spot repairs (welding) on the left side, but both tanks appeared to be very solid and were definitely not leaking prior to removal (no smells, no staining). but during the final acetone wipe down I noticed what looked like tiny pinholes on the bottom of both tanks, and sure enough they were. Apparently the alloy was thin enough that the pressure washer blew through in a few places.

So I'm looking for recommendations on shops to repair my current tanks, or would consider new tanks if they are available ($$$! I imagine). Used tanks are not interesting as I've learned you can't really tell how solid they are from the outside if the textured coating is present.

 

FWIW 308 fuel tanks are aluminum.

 

Yes, obviously. Doesn't mean they can't corrode. In my case it appears from the inside out. Probably related to the large amount of time the car wasn't driven in the last dozen years.

 

Pin holes / general corrosion in the bottom of the older Ferrari fuel tanks is a very common occurrence. You need to cut out the affected areas, weld in new plate and pressure test the tank. Not an easy task for the average aluminum welder but perfectly feasible. In other words, repairing is the preferred way to go if the affected areas are limited in size and if (And only if) you know a trusted welder that are experienced with working in old "contaminated" aluminum. Otherwise buy replacement tanks. Nothing wrong with buying used tanks if you make a thorough pre-buying inspection from the inside of the tank.

Best, Peter

 

So after pressure washing the textured material from 4 tanks (my two original and two purchased from different sources) I've learned that tank corrosion can occur on the upper parts of the tank as well, and on the outside. In fact after close inspection all four tanks had corrosion in various places on upper surfaces of the outside even though the textured coating looked just fine before removal. I noticed that where the alloy appeared very healthy, the texture stripped easily and cleanly, and where it left small clumps of residue there would be the corrosion. My conjecture from this admittedly small sample set is that most all these tanks are quietly corroding away under that pretty coating. And until they corrode enough to actually start leaking no one will be the wiser. A couple of photos from two spots towards the top of two tanks illustrate this outside-in corrosion. In both photos I've lightly cleaned the surface with a hand held abrasive pad, and while there are no perforations, some of the pits appear to be at least 50% of the panel thickness deep.


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Wow, very interesting and thank you... pictures tell a thousand words. After the pinholes are addressed (e.g. welding sections) would POR-15 be a viable option to help ensure sealing and (hopefully) perclude additional corrosion?

 

I'm researching tank sealants at the moment, as I just can't imagine putting the tanks back in without some sort of comprehensive solution. I store my cars in a garage under my house, so I've redone all of my other hobby cars with new tanks in stainless or alloy to allow me peace of mind. Sadly not an option here.

 

I believe the tanks suffer from galvanic corrosion because they are aluminum and they are mounted in a steel car.

I have replaced both tanks in my gt4 a couple of times in the nearly 40 years I have owned it (with secondhand tanks). The good news is that if you have collected secondhand tanks as spares, they don't corrode outside the car.

Last time I looked new tanks were available at around GBP1K each.

 

I can't find new tanks anywhere for the GTB/GTS. GT4, yes.

 

What about an epoxy resin two pack coat ?

Just flying flags guys don’t bite my head off .I had a 8 gallon military style Gerry can ( was stud on bare earth ) developed pin holes in its base .Roughed up the surface and built up a few layers exterior of twin pack epoxy .Been fine ever since .Obviously the failure mode was just seeping into the ground .Not as potentially damaging as weepy tanks on a GT 4 with the hot exhaust down stream in the line of fire etc .

 

I would think replacing aluminum sections would be better than epoxy - it just seems like a bandage that will eventually unstick. Sure there are impurities but if properly treated and ground out before welding, most of those would be taken care of to a certain degree. I'm not a welder but I watch people do it a lot so take my advice with a grain of salt. If you're not really a concourse guy, go get something new made that fits and works from a local fab shop.

 

The aircraft grade coatings (internal and external) have very good track records when applied correctly, (which is the trick with all coatings, really). Welding in new patches for the tank bottoms could make sense, but there are dozens of deep external pits in random places all over the tanks, and I think you'd still want an internal coating to be sure there were no residual pin holes in the welds.

I'm exploring have new tanks made, but my go to solution (Andy Wiltshire in the UK) who does beautiful work is far too busy doing vintage English stuff that he has no motivation. The main halves for each tank look to be machine deep drawn, so hand made replicas would be very time consuming and take a high degree of skill. If I can find the right talent I would be willing to fund the manufacture of 20 sets or so, but the end product would need to be indiscernible from original or I'm afraid there would be no takers.

 

Not sure if this is one of what you are looking for?

 

Yes, but not actually available from them at the moment, and no expected dates.

 

I posted a similar post in another thread about fuel tanks a few months ago, but I had the fuel tank in my 240Z sumped during an EFI conversion, which caused it sweat out a bunch of lead sealer on its pinch seam around the whole edge of the tank. It would slowly seep fuel -- very not good. I was about to throw the tank in the trash and start over with a fuel cell.

Before doing that, I did the POR 15 fuel tank repair kit on it: https://por15.com/products/fuel-tank-repair-kit Don't get me wrong, it was a LOT of work doing the kit right, but the result has been fantastic. The tank has been completely sealed with no leaks for 5 years now, has done thousands of miles on hot and cold days, and generally sits with a completely full tank of E10 premium or whatever they normally have at the gas station, in my shop. I would definitely use this kit again, and personally I think it would be a more than reasonable choice in this situation rather than going straight for new tanks.

 

I think a big challenge to coating the inside is getting even coverage. Doesn't the OEM tank have a bunch of internal baffles?

 

That's a bummer. It says "In Stock" too.

 

One of the reasons there is so much work involved, is the amount of time you have to spend rolling the tanks around to ensure coverage. You end up taping the tank shut with the sealant inside and rolling it around for 20 minutes prior to draining it and letting it sit for 96 hours. I would imagine if you're rolling it in every direction for the prescribed amount of time you'll do a thorough job getting all of the baffles

 

Interesting to hear the treatments here. I would want to understand if the ethanol added into car gas would have any impact. Avgas is usually ethanol free.

 

The place to find custom tanks is the Boating Industry.

I would think with careful planning and your old ones as patterns, fresh metal all around is the way forward??

 

Checked via email with them this morning and was told they only have the Australian version available from stock, which appears to not have an opening for a gauge sending unit on the left side. I was able to put the one you recommended into a cart and check out, so will see what happens.

 

You can easily repair fuel tank leaks with an aviation product called Proseal. It works very well.

 

A few minor mods on a new tank would be well worth it., IMO.

 

So an update: Maranello Classic (ferrariparts.co.uk) sells new tanks, but only in the Australian version at this time. In asking them to check some of the details for me, they discovered they had 1 American version (left side) still in stock, which I purchased. The Australian versions appear very similar to the U.S. spec, but appear to only have the one vertical mounting strap.