twin tank venting

[360gts]

Trying to find the thread on this topic...not having much luck.
Does anyone have information on the service bulletin that covers this???
Looking at my cars (my 69, and both 67's have it installed at the factory)...my 65 looked like it was dealer installed....

[swifty]

Got these pics

[360gts]

That looks like dealer installed (same as my 65)...does the service bulletin say that this was to be done on ALL cars with twin tanks?
My other cars have different tabs for the pipe on the RH side.

[MiniMark1]

Hi there - I have a Serck right hand tank and have vented the tanks in the standard way - i.e the pipe vents through the boot floor on the same side as the tank - what is the benefit of crossing over the vent pipes?

Many thanks

Mark

[Pete]

It was to help prevent siphoning the fuel off if the car was parked on a tilt if I remember correctly?

[Andrew1967]

Got these pics

I thought I recognised that picture Swifty

Dermott, that wasn't dealer installed but I think I did a reasonable job of it

[360gts]

You sure did...it looks exactly like my 65 which was dealer installed..a grand job you did.
So, back to my original question....did the service bulletin cover ALL S models retrofitting all the way back to 970/1070s with the optional RH tank?.....I know why it was done etc...

[swifty]

Got these pics

I thought I recognised that picture Swifty

Dermott, that wasn't dealer installed but I think I did a reasonable job of it

Yes I used these pictures as a reference for my own re- builds .... Cheers ... Ken

[MiniMark1]

Thanks Pete - think I'll leave mine as is then.

[Nick W]

Excellent this is just what I was looking for!

Do we know what clips/nuts were used at point A?

Any images of factory installation?

[Andrew1967]

I'm pretty sure I used a W shaped clip (one half either side) that are used to secure the two servo brake pipes together and fitted it using the screw (or stud) that holds the rear seat squab into place.

Will check on the car tomorrow.

[Johnny]

Factory right side clip on my August built 65 S. Upper left and right side clips are the same, held on with nut threaded to seat frame stud.

[AndyPen]

Thanks for the pics Swifty, I had totally forgotten that mine were originally like that.

I think I had those screw holes welded over - darn another mistake! Must check on my shell later.

Clips wise, didn't they use the same as the brake servo ones at the top?

[Nick W]

Johnny...great image of your 65s vent pipes

Any one got images of post 66 factory set up with the welded on tabs?

[Johnny]

Here are tabs from an unrestored November 66 build.



A little mangled.


These are from a March 67 car.

[Nick W]

perfect... thanks Johnny

[Peter Laidler]

Food for a bit of thought and nothing to loose sleep about and thinking out aloud as I'm prone to do, I was never convinced that these vent tubes in each tank served any purpose - except for one, below.
There doesn't seem to be any way that these vent tubes would prevent or even enable self syphoning. After all, the top of the vented filler cap is (at a guess) 1/2" below the highest point in the tank - where the vent pipe enters the tank. And of the car were left at a daft angle, with two (or even one) full-to-the-brim tanks*, the fuel would be pixxing out of the filler neck by then. And if you vent a syphoning operation, guess what happens?
They don't vent anything when the tank is being filled up, because the cap is off
They don't vent anything as the car is running, because the fuel filler cap is vented and allows sufficient air to enter the tank to replace the fuel
They don't cater for the expansion and contraction of the fuel or other atmospheric causes, because the fuel cap is vented sufficient to allow for this slow operation.
The only way these vents serve any useful purpose is when you are filling the, say, left hand tank (filler cap off....) which allows fuel to cross-feed into the right hand tank (cap ON). At this point, fuel is being fed into the r/h tank faster that the fuel cap venting can cater for - although it will eventually.

But that's my take on the real usefulness of them in a single tanked car. Maybe there's something in the construction and use regulations. Or are the vent pipes just a secondary valve in case the filler cap vent fails for some unknown reason? But they're there and we fit them!
(*don't forget that you can only fill the tank to the BOTTOM of the filler neck opening)

[Twincam]

I think many Mk1 saloons came with unvented caps and all the tubing is primarily for venting and tank balancing.

[Andrew1967]

I think many Mk1 saloons came with unvented caps and all the tubing is primarily for venting and tank balancing.

Estates and commercials would have vented caps and saloons are non-vented.

I wouldn't advise using a non-vented cap on a non saloon car unless you want petrol pissing out everywhere. Found this out on my pick up

[gogsymac]

Factory right side clip on my August built 65 S. Upper left and right side clips are the same, held on with nut threaded to seat frame stud.

Johnny - are the vertical clips down the side of the right hand tank pop riveted in place or held in place with a self tapper screw?