Project Theseus

[Noll]

Diff cover is aluminum. Polish it!

Yeah, In suppose I could, I'm leaning towards silver hammered-finish paint though to match the struts, control arms, and strut tower bars.


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So, figured I should have a peek inside my fuel tank to make sure the inside condition matched the outside (which is pretty darn good). Spoiler alert, it doesn't:



The bottom of the tank and about 1" up the walls is like this, everything else is perfect in there. This is still very much a bit of an issue though.

I suppose my options are:

- call a radiator shop and see if they'd take it on and what they'd charge
- throw some gravel in there, try to knock all the loose stuff off, and use a fuel tank coating kit to seal it
- cut the tank in half at the seam, clean it out with a wire wheel on an angle grinder etc, and re-seal
- ditch the stock tank altogether and get a fuel cell (might have to remove the spare tire well for this, but that's not a huge deal).

Any thoughts? I'll be starting by stripping the paint off the bottom of the tank to see if there are any pinholes visible.

[zedfoot]

I had mine done at a gas tank shop about 15 years ago. They did a nice job, but it finally failed at the seam. Because it was dented from a mishap with a floor jack, I cut it in half at the seam to straighten it out, and wire wheeled the old liner off, which was peeling. Brazed it back together, but I would do it differently next time. If anyone has a ratty tank, any condition, I would buy it to experiment on.

[Noll]

I had mine done at a gas tank shop about 15 years ago. They did a nice job, but it finally failed at the seam. Because it was dented from a mishap with a floor jack, I cut it in half at the seam to straighten it out, and wire wheeled the old liner off, which was peeling. Brazed it back together, but I would do it differently next time. If anyone has a ratty tank, any condition, I would buy it to experiment on.

Good to know! where exactly did you cut (if you happen to have pics, even better)? if I go that route I'm debating between just above the flange, or trying to separate the flange itself and reattach after.

[Noll]

Minor update, pulled the fuel sender out again to see if it was usable at all. It was covered in crud, sediment, varnished gas, and who knows what, but after some wire-brush cleaning and some sandpaper on all the contacts it seems to read correctly throughout the whole travel (10-90 ohms). I'll get a new o-ring and rock it for now, if it proves unreliable it's not too much of a pain to swap a new one in at some point.

Maybe I'll get lucky and a lot of the tank crud is just sediment and varnish? Here's hoping.

[zedfoot]

Good to know! where exactly did you cut (if you happen to have pics, even better)? if I go that route I'm debating between just above the flange, or trying to separate the flange itself and reattach after.

The last photo of my first post shows how I had to cut it. No way you will be able to separate the layers.

[Noll]

The last photo of my first post shows how I had to cut it. No way you will be able to separate the layers.

Yeah, the "zippered" seam seems pretty close in on the flange, so will want to cut above that point if I go that route.


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Tank update. First up, good news, I poked around at the bottom with a metal rod and it seems to just be about ~4mm of sludge and crud as opposed to rust. Phew. Going to wait to hear back on a quote from a local radiator shop for cleaning, and if that's too pricey I think I can get good results DIYing it.

Started to clean up the exterior to see how it really was in relation to the exterior. The whole tank had this rubbery coating on it, definitely had been sealed or something by someone before.




Pulled off a lot of it and didn't notice anything untoward in terms of rust, some minor pitting but nothing big.




The one thing I did find was this patch, which seems a bit sketchy but doesn't seem to leak any (some gas left in the tank so I flipped it over to test). If I end up doing the tank refurb myself I'll either epoxy over the seam just to be safe, or cut it out and redo it. The sharpie marking on the top of the tank is not mine - I assume a previous owner got a junkyard tank after the car was rear ended or a radiator shop or similar marked what it was for when they did the coating.




The bottom is in nice shape, no big dents etc.




Once I hear back from the rad shop I'll ask them if their hot tank will remove the coating too (would save me work if I go that route), if not I'll tear the rest of it off.

[Noll]

Painted some more stuff today, I think other than the fuel tank and the stuff I need to buy still (hardlines etc) that should be pretty much everything ready to go on once the underside of the shell is painted. I know I'm missing a couple of the brake line clamps but I'll make those when I assemble everything so I don't make ones for the wrong spots.

[Noll]

Stripped the bottom of the shell, and started on the painting.




First coat was mostly just on/around seams, once this cures I'll apply seam sealer then do a 2nd coat on everything properly.







I think I have enough paint to do all the underside and interior, but in order of priority I'll be painting the underside, the inside of the floorpans, and then the rest of the interior. If it comes to it I can always do the rest of the interior later, the high-foot-traffic spots are the most important for now for that extra strength (vs using just spraypaint).

[Noll]

Seam sealed and painted the shell today inside and out, pretty happy with the end result. The brush marks should even out as the epoxy cures, and I'll be spraying some sound deadening in the wheelwells and a couple other places to avoid tinniness.








This half of the paint went farther than the first which was nice, was able to get all the interior done too:






I also did some stuff to the gas tank while waiting on the seam sealer to dry, poured a bunch of heavy-duty cleaner in and a couple bolts and shook it around for a while.






It did enough to show me that the bottom of the tank seems it be in good shape, so that's nice. The radiator shop asked for some more pictures and info on the tank, so I've sent that off to them and am waiting to hear back. There do seem to be a couple of pinholes near the top of the tank (I think from moisture trapped between the coating and the tank on the outside), but nothing major. Also, interestingly, the patch on the tank looks normal on the inside there, so my assumption is that it was put on over some pinholes. With any luck the rad shop won't mind this, I can always braze/solder over the pinholes if they don't want to once the tank has been cleaned.

[grannyknot]

What epoxy paint are you using on the bare metal? Looks fantastic!

[Noll]

What epoxy paint are you using on the bare metal? Looks fantastic!

Many thanks! It's an industrial epoxy, Devoe Bar-Rust 235 (comes in a bunch of other colours too, and can be sprayed as well as brushed):

https://www.devoesuperstore.com/devo...ss-black-1g-34

From the MSDS:

For use on properly prepared steel or masonry surfaces including immersion (non-potable water)
service. Ideal for structural steel, piping, storage tank exteriors, machinery, and equipment in petroleum
refineries, pulp and paper mills, chemical and fertilizer plants, and sewage treatment plants

It's designed to hold up to a lot worse than I'll be asking of it, and a friend of mine applies Devoe epoxies to snowplows in the GTA and says it holds up great, so I'm pretty confident it should work for my use. It's designed for applications when there's imperfect prep, which is part of why I went for it - I did my best to clean the bottom of the shell but wanted to know i wasn't going to get peeling if I missed a little bit of surface rust in a corner etc.

[Noll]

After letting the epoxy cure for a few days, I put the rubber floor plugs in and sprayed a bunch of stonechip protection/ sound deadening on today:











It's not a perfect, run-free, exactly-as-factory finish, but looks half decent and a hell of a lot better than before:






The brake/fuel lines and some other misc stuff should show up next week, so that will be the next job. In the meantime I'm going to design/3d-print a bunch of the transmission-tunnel mounts that go in the body brackets in flexible rubber filament.

[Noll]

Started on the designing/printing today, made up a mount block for the feed/return lines from ABS:

[Noll]

More little stuff today.

Technoversions diff mount arrived, and test fitted. Had to do a little hammering because the exhaust-tubing bracket's thickness was enough to push the opposite edge of the mount out and cause it to hit the transmission tunnel before the bolt holes lined up. All fits nicely now though, I suppose that's a 260/280z specific issue due to the hangar location.






The 3/8 tubing also showed up (the 5/16 and 3/16 will be here tomorrow despite being shipped from the same place), so I ran that. I'm currently printing V2 of my ABS mount, the curves in the tube overlapped with the mount and caused the halves to be forced apart a bit when it was bolted up with the tube in it. v2 will be a bit thinner (~8mm) on that axis to avoid that.

I also came to the conclusion that the cheap bubble flare tool I got for flaring the fuel line ends for the softlines is not up to the task for the 3/8 stuff at least- it just kept pushing the tube out instead of flaring it. My local Napa is going to kitbash some compression-fitting-to-hose-barb fittings, they had to order a bit in but they'll be ready tomorrow. I've also decided to end these lines right at the end of the transmission tunnel before the engine bay - once the car is the right way up (and the engine bay is painted) I'll run a hardline the rest of the way and join them with compression fittings.
This will save me a lot of aggravation trying to get all the front bends right in a long-ass bit of tube, and will mean less masking off required for painting the engine bay. Will do the same with the brake line with a basic brake line union etc.

[Noll]

Printed the revised rear fuel line bracket:




And designed and am in the process of printing the transmission-tunnel mounts:



I had to change plans a bit with these, the flexible filament I got ended up being TOO flexible for my printer to print even with modifications. I could get some less flexible stuff and try again, but that's 50$ and a bunch of waiting.
Instead, I opened the holes up on the mounts by about 1.6mm bigger than they need to be, and plan to use multiple layers of heat-shrink tubing over the hardline at every junction where it clamps into the mounts. I think this should do just fine for the purpose of vibration damping and making sure no stress fractures develop over time, but if someone has good evidence to the contrary let me know, like most people I much prefer not being on fire.