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RE: [T3] As the Tank Turns - this weekend's episode

> -------- Original Message --------
> Subject: RE: [T3] As the Tank Turns - this weekend's episode
> From: Jim Adney <jadney@vwtype3.org>
> Date: Tue, May 09, 2006 10:41 am
> I'm not exactly sure what you mean here, since I believe that all of the tanks 
> had a vent port (the medium sized port, maybe 12mm.) IIRC, the location of that 
> port moved in mid-'68. There were additional small, 3mm, ports that varied more 
> over the years. Those include the ports for the EEC.
> If you have a tank that has a round filler port plus a medium port, then that 
> is probably a late 68 or 69 tank where the actual tank vent comes off a Tee in 
> the medium port line and there is no other port. Later systems used that same 
> Tee together with a small port, and then a second small port was used for the 
> overflow cannister under the LF fender that went with the charcoal cannister & 
> EEC system. There were a number of variations, so I may not be remembering this 
> exactly right.

OK, let me restate/clarify.  The 70 and 71 tanks have a vent port on the
opposite side of the tank as the filler (the round ones) and overflow
ports (i.e., filler are on the right side, vent on the left side, all
three above the seam/flange)

The 1968 tank I have has the oval (larger diameter) filler port and the
overflow port, but no vent tube attached to the tank on the other side
from the filler.

The 1969 tank has a ROUND filler port and overflow port but still NO
vent attached on the tank on the other side from the filler.

therefore the 1969 tank would work in the 71 and later cars with the
round port. The 1968 tanks will not work unless you make a change to
the filler hose.

I think we're saying the same thing here, but I was only mentioning what
was welded on the tanks, not that there was or was not a venting path in
the system.  Yes there was a small vent off the overflow tube on some
models.  But the difference was that it was in the tube and not part of
the tank.

My original assumption was that when the filler port changed, that the
vent changed also... which was not evidently the case.

> I haven't noticed this, but you may be 
> right that they varied a lot. That seems odd, however, since I would expect 
> that the "jet pump" action of the returning fuel would only be effective if the 
> alignment was pretty good.

I would have thought that there would be more precision required for
this to work also... but water flows from the outer area into the cup
with NO problem just using gravity alone in the tank that is only
slightly off-center.

The other tank that has the return pipe mostly covered seems like it
would cause more problems... from the factory.  I may try an experiment
and drill the cup by inserting a drill bit up the return port and see
how well that tank performs.  Just because it's a good tank otherwise. 
It will at least be good for a carb-conversion car.  ;)

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