I did the POR-15 route. Here's the before and after- (I've posted this before) I wasn't dealing with as much as you are. The POR treatment took care of the surface rust before the final sealing.
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Can you provide more detail? Are you saying the base of the sock seals the inlet tube to the tank? What does/did the factory use to seal this?

(Sorry for the hijack, but I'm about to embark on the same project.

I have to say that I'm a HUGE fan of the POR-15 system. My only advice is that you use nits/bits of iron or something ferromagnetic when you shake it around (or did you already do this? I might have missed it). The only reason is that when I treated an old tank I skipped over that part and used rocks and couldn't get them out after the thing had been cleaned.

The good part is that the sealant is strong and thick and it just made the rocks a permanent part of the inside of the gas tank.

I patched several holes that were more than 1/2" in diameter with JB-Weld after treating the inside of a tank, coated the inside, and then drove 5000 miles, before hitting a big rock (this was in the Caddy and the tank was exposed under the trunk of the car) and knocking another hole.

That stuff works fantastically - and if you're worried about bare metal, just make sure you use their whole system, including the finish coat - it's like rustoleum and will keep the rust from coming back...

You've got it. Basically the base of the sock is a crush washer (single use). It deforms when you install it. So the factory didn't have to use sealant, and you don't either if you use a new one.

Those strainer socks are readily available from the usual 914 parts suppliers.

Now if I could only get my hand in the tank!

It is installed from the outside.

Hmmm, good thing I didn't force my hand in there to pull it off! Thanks

take off the capturing nut on the supply tube and the tube will pull out. the stainer will either come with it or you'll have to persuade it out. do not ruin the fiber gasket either.

k

Those are my pics. You're all welcome to them.

A couple of lessons learned by me-
regarding the flash rust (great term)- When I completed step 2, I rinsed it by putting a hose in one of the big holes on top. I let it spray with both tubes off at the bottom. The combination of running water and air flashed stripes of rust going down the inside of the tank, and I had to do step 2 all over again. The next time, I kept the bottom holes plugged, and rinsed by filling the tank full, then draining it quickly. I did it 3 times to flush it, and no rust. I'm guessing the lack of air slowed down the rust action.

after step 2, I put the vacuum hose from my shop vac into the filler hole on top, and put the end down to the deepest section of the tank. While it was sucking, I blew into the fuel level sender hole with my heat gun on medium. It worked great. I could feel the bottom of the tank heat up, and I could see the wetness disappearing when I peeked in around the heat gun with a flash light.

When I removed the tubes on the bottom and the sock, I munged up the thread on one of the nipples. It was a pain with magnifying glasses and jewelers files to clean it up, so be careful. Also, I learned that the nut is aluminum- very soft and easily damaged. I got new ones from Stoddard- they had to backorder from Germany but they came in about a week for only maybe $3 or so each.

This one will be controversial- To seal the tubes and the sock, I installed them while the POR-15 sealant was still wet. It's now TOTALLY permanent, but I didn't want to fool around with leaks, and, after 98000 miles and 30 years, my sock was still OK (replaced it anyway), so what the heck.

Good luck!
Jim

nice write up jim. how i dried my tank after draining the water...on the bench top with a elec space heater pointed at the fill/sender holes. warmed the whole surface of the tank in about 30 minutes. bone dry in an hour. this worked well for a bit of warmth to the tank prior to ext painting.

k

A hair dryer in the filler hole worked for me. About 30 min and the tank was dry.

Use new washers and it shouldn't leak when you fill it up again.

Well I just finished the last of my acid with the tank completely full and got all the rust out. I put it in the sun with the shopvac on blow and the tank upside down on some sawhorses and dried it out in less than a half hour, but it instantly flash-rusted.

So is that normal? (asking the non-sealer guys, considering the rest of you are crazy about cleaning and sealing it with the kit).

I would follow up the acid treatment with a Phosphoric Acid treatment.

This will leave a coating of Iron Phosphate on the inside exposed metal surfaces and will help to reduce the risk of flash rust.

I am a proponent of coating the inside of the tank, so after phosphatizing the tank, I would coat it.

In Florida it is... Your shop vac is just blowing wet air.

Colorado is drier than a popcorn fart. Once again, I pick mine up from the rad shop, paint the exterior and toss it in the car and fill it with gas and go.

Doesnt the coating kit come with phosphoric acid as the cleaner? I'm starting to lean towards coating the tank considering it isnt exactly driven around all the time.

I went and got a new strainer sock for the tank...

So the tank is all cleaned out and I installed new hose under the tank:

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Then installed tank, fuel gauge, expansion chamber...

You may have the hoses get kinked after the first drive. You'll notice when the car dies.

If that happens, safely raise the front of the car, and remove the lower cover, then pull the hoses out of the access hole and carefully reinsert them making sure they don't kink.

Good luck! I think you're close!

I made sure all that extra hose was looped, not kinked, so hopefully we dont have that problem.

I would hold off on filling the tank to the top. Fill part way then start the car and drive for a short distance then, If everything is tight and no leaks, fill the tank.
One thing I like to do when the tank is out, is move the pump and fuel filter to the side of the front trunk area, on th eearly 914s even on a 75-76 914. That way if you have to change the filter. You do not have to jack the car up. Trust that the jack stands will hold and slide under the car, loosen the hose clamps, gas dripping down, remove the old filter and gas dripping down, install the new filter and tighten the clamps.
You can mount everything in a secure and safe place.
CCLIN914NATION

So is the best place to mount the pump/filter under the tank in the cavity? Mine is currently underneath the car behind the "skid" plate rather than in the confines of the gas tank body cavity. It had previously been relocated. It seems it would be easier to get to from underneath when replacing?

The early 914s 70-74 had the pump and filter mounted at the midsection passenger side, near the heater tubes. Good place to casue vapor lock and heated fule problems.
The 75-76 pumps and filter were mounted as you see in teh previous pics, under the tank and the pump secured to a small access cover that you pull out, through, and into the front trunk area.
This is the better of the factory locations, IMHO.
But, if you have the tank completely out, I prefer to move the pump and filter into the side wall area in the front trunk.
I will try and post a pic.
CCLIN914NATION

Definately. I have the gear stack out right now, so I'm not putting anything in there yet. I'll probably put a gallon or two in of regular (see my poll/thread about gas grades) and see how that runs and adjust accordingly.

If you are concerned about "Muriatic" (Hydrochloric) Acid,... just go down to the supermarket and buy a couple gallons of white vinegar. It will work more slowly, but the acid WILL still dissolve the rust.

Nuts and Bolts, shake it repeatly.

NEUTRALIZE the acid with BAKING SODA!.
Rinsing with water will not neutralize the acid and it is heavier than gasoline, so will stay in the bottom of your tank, eating steel.

Now you prepare that Fetzer valve with some 3-in-1 oil and some gauze pads. And I'm gonna need 'bout ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State.