356 Fuel Cock Disassembly

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Ron Schramm
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356 Fuel Cock Disassembly

#1 Post by Ron Schramm »

I made a simple homemade backing block to enable easy disassembly / reassembly of the 356 fuel cock. When the valve sits dry, like mine did for 39 years, a rebuild of the cock assembly or replacement is required. The rebuild kits are much less expensive than the cost of an entire new valve assembly and the kits include all of the critical wear items.

Here's a video to illustrate what's in there and how to disassemble:
https://youtu.be/gGzSX3dqQRk
Ron Schramm
Escondido, California
'63 B coupe

robert moglia
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Re: 356 Fuel Cock Disassembly

#2 Post by robert moglia »

Very helpful, thanks!
Check out my progress! “Bob’s 356A project”
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John Brooks
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Re: 356 Fuel Cock Disassembly

#3 Post by John Brooks »

Do another when you reinstall it on the showing how to seal the washer and explain the double threaded nut. That is usually what I need to fix after someone rebuilds their valve.
John Brooks

62 Roadster
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getting pushed around in porsches since 1965

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Ron Schramm
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Re: 356 Fuel Cock Disassembly

#4 Post by Ron Schramm »

John Brooks wrote: Thu Jul 27, 2023 10:57 am Do another when you reinstall it on the showing how to seal the washer and explain the double threaded nut.
Good point. It can be a bit of an adventure to reinstall the valve to get your head around the double threaded nut to fix the valve to the tank!
Ron Schramm
Escondido, California
'63 B coupe

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Harlan Halsey
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Re: 356 Fuel Cock Disassembly

#5 Post by Harlan Halsey »

An alternative method of disassembly and assembly is to compress the unit with a drill press. That way the critical surface is horizontal and you can see what you are doing.

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Marcus van Bers
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Re: 356 Fuel Cock Disassembly

#6 Post by Marcus van Bers »

John Brooks wrote: Thu Jul 27, 2023 10:57 am Do another when you reinstall it on the showing how to seal the washer and explain the double threaded nut. That is usually what I need to fix after someone rebuilds their valve.
So what is the procedure for the double threaded nut. Do you start one first, or start threading both at the same time? How best to make sure the washer is properly sealed against the tank opening? I'll be doing this shortly.
63 B Karmann Coupe
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Martin Benade
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Re: 356 Fuel Cock Disassembly

#7 Post by Martin Benade »

If you get one side of the nut barely started, and then continue turning it as it screws onto the second side it will draw the fuel cock tight to the tank. It’s actually pretty easy. Hold the fuel cock in alignment as the nut tightens it down against the sealing washer.
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Marcus van Bers
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Re: 356 Fuel Cock Disassembly

#8 Post by Marcus van Bers »

Martin Benade wrote: Tue Aug 08, 2023 10:41 pm If you get one side of the nut barely started, and then continue turning it as it screws onto the second side it will draw the fuel cock tight to the tank. It’s actually pretty easy. Hold the fuel cock in alignment as the nut tightens it down against the sealing washer.
Thanks Martin. I'm currently driving the car around when the sun comes out so I can use up the gas and minimize how much I have to drain. Seem to have more rain days this summer.
63 B Karmann Coupe
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Ron Schramm
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Re: 356 Fuel Cock Disassembly

#9 Post by Ron Schramm »

Marcus van Bers wrote: Tue Aug 08, 2023 4:01 pm
John Brooks wrote: Thu Jul 27, 2023 10:57 am Do another when you reinstall it on the showing how to seal the washer and explain the double threaded nut. That is usually what I need to fix after someone rebuilds their valve.
So what is the procedure for the double threaded nut. Do you start one first, or start threading both at the same time? How best to make sure the washer is properly sealed against the tank opening? I'll be doing this shortly.
I may do another video when I install my new fuel tank. But it likely won't be better than this Heidi & Franny video:
https://www.youtube.com/watch?v=FB4rLkIoIVU

As you are aware the nut that secures the fuel cock to the tank has 2 sets of threads, one left hand and the other right hand. The fuel cock body has left hand (i.e. reverse) threads on the body. The fuel tank has normal right hand threads. The end result is that, as Martin has pointed out, above, getting the reverse thread nut just started on the fuel cock body (I use one turn of engagement) prior to installation allows for maximum thread engagement on both the tank and the fuel cock when tightening the assembly to the fuel tank. This also allows me to confirm that the nut is not cross-threaded on the cock body. The dual thread configuration causes the nut to draw the fuel cock body to the tank fitting and crush the sealing washers as the nut is tightened in the normal 'righty righty' manner. It is worth noting that it can be a bit fiddly to get the nut aligned to the tank threads to get a clean thread start on the tank given the location and proximity of the steering damper, brake lines, etc. Several tries may be required to be successful.

A couple of things worth noting as long as you are already in there:

1) As shown in the video, make sure to fit the fuel cock handle / lever so that everything is properly aligned prior to tightening the fuel cock/tank nut.
2) As long as you have the fuel cock removed this is a convenient time to flush any debris that may have found its way into the fuel tank. I clamp a length of 3/4" I.D. heater hose onto the fuel tank fitting that drains into a bucket on the floor and pour a gallon of gas thru the tank. I do this 3 or 4 times if I see any debris in the drained fuel. To capture the debris I tie-wrap a paper paint strainer to the free end of the 3/4" hose to collect / clear any debris. Once everything is installed and secured I just pour the fuel back into the tank.

If you are not familiar with paper paint strainers, the paint strainer I am referring to is generally available for free at your local automotive paint store; Like this one for sale on Amazon:
https://m.media-amazon.com/images/I/41P ... L._AC_.jpg
Ron Schramm
Escondido, California
'63 B coupe

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