Gas tank question

[jpearson]

I am pulling the gas tank from my 1975 911s. The car has sat for years and the previous owner told me that it used to "run rough" when the tank was less than 1/2 full. I drained the tank last night and when I look inside there is obvious rust throughout. I have a couple questions:

1. I found a radiator shop in town that will boil and coat the tank for me. Are there any problems with this for a stock 1975 911s tank?

2. Does my tank have a swirl pot? I read in another post that the swirl pot is a contraindication to coating the tank. If I have a swirl pot what are my other options?

3. How does the POR15 gas tank kit compare to having it boiled? The turnover time at the radiator shop is 1-2 months and I am a little impatient so I was thinking about doing it myself. Any other products that people recommend?

4. The radiator shop certainly doesn't specialize in Porsches is there anything I should make them aware of or that I should do myself to prepare the tank? Any special preparation for the POR15 treatment?

Thanks - I know that was more than a couple questions but as always your input is appreciated.
Josh

[ossiblue]

Yes, your tank has the swirl pot. Proceed with caution.

[Evans, Marv]

If the radiator shop had that much turn around time, I'd definitely shop around. The POR-15 kit comes with a tank cleaner, but I would get it boiled out instead and coat the inside with POR-15 afterwards. Their tank cleaner is good for scale but if it's worse than that, getting the inside professionally cleaned is much better.

[RWebb]

getting it "boiled out" will likely destroy the swirl pot

be sure they know what they are doing and do not harm the plastic swirl pot

[Ionizer]

Sounds complicated and expensive to me. Why not use it as it is? A little rust on the inside doesn't matter.

Can't imagine it has anything to do with the problems with the rough idle. Other than maybe a clogged pre-filter (on the tank drain plug).

When it finally rusts all the way through just get a new tank.

[jpearson]

Thanks for the input. After a little research and talking with people about coating products I think I am going to try and derust my tank with electolysis and then coat with something transmision fluid or wd-40 until I can fill with gas and get it back in the car. I'll post some pics of the progress. Your opinions are appreciated.

[vash]

i took a really bad 75 tank to a radiator shop. they cleaned and sealed it for me perfectly. i dont remember it being too expensive.

they had to drill and tap a small hole in the corner to get the excess material out. i have had no issues in the many years since being done. (bro has the car now)

my tank was BAD. fuel varnished.

[timcantrell]

I don't replay to a lot of these, but this one deserves a response. I had the exact same problem with a 75 911S tank. The rust in your tank will be your worst nightmare for your fuel system and injection system. It will cause rough idle, rough running. Take it to a competent radiator shop. IF the rust is not bad, do not have it coated after boiled out. Sometimes the coatings will not last and once they start coming off, they are as bad as the rust. Once a competent radiator shop is finished, the inside will be as shinny as the outside, all paint and rust will be gone. You will need to repaint the outside. If you have run your engine with this rusty tank, you will need to replace the fuel filter, blow out the fuel lines and clean all injectors.

[wayner]

Does the same rad shop advice go for oil tanks?

Mine was painted and left to collect dust and who knows what when the prev. owner began this project. I'm afraid to use it until I am sure it is clean.

Thanks in advance.