Fiber washers versus o-rings

[Jon Schmid]

Hi all,
I'm just curious, would it be better to continue to use new original fiber washers to seal where the fuel line banjo bolts connect to the tops of Zenith 32 NDIX carburetors or use fuel resistant o-rings instead?
Thanks in advance for any input either way...

[Martin Benade]

O rings will squeeze out from that type of fitting as you tighten it. The original washer is really the only way to go.

[Phil Planck]

Orings are meant to fit in a gland. You probably would have to make a larger banjo fitting and machine in the appropriate size gland for the chosen oring.

[Jon Schmid]

O rings will squeeze out from that type of fitting as you tighten it. The original washer is really the only way to go.

Thanks, Martin. I wasn't thinking of torquing the bolt down too much. Maybe putting the o-rings under the washers? I'll gladly punt if this is not the way to go--thanks again for your input.

[Ron LaDow]

O rings will squeeze out from that type of fitting as you tighten it. The original washer is really the only way to go.

Thanks, Martin. I wasn't thinking of torquing the bolt down too much. Maybe putting the o-rings under the washers? I'll gladly punt if this is not the way to go--thanks again for your input.

If they are torqued tight enough to seal, they will extrude out the side. Light enough torque = no seal.
You really should have no problem with aluminum crush washers if the sealing surfaces are OK.

[Jeffrey Leeds]

And on current generation Porsches the factory, in fact, identifies the aluminum crush washers as "sealing rings"

[Jon Schmid]

OK, thanks for the input, guys, I appreciate it.

[Martin Benade]

Are the aluminum and fiber washers interchangeable? I feel more comfortable with fiber on pot-metal carbs and fuel pumps as I imagine less torque will make them seal.

[Ron LaDow]

Are the aluminum and fiber washers interchangeable? I feel more comfortable with fiber on pot-metal carbs and fuel pumps as I imagine less torque will make them seal.

Apologies if this is too elementary:
Most banjo joints rely on a sort of 'class 1' thread; it has to be loose enough that all the elements will find a happy medium and parallel sealing surfaces. So if the surfaces don't have scratches, the metal (Al or Cu) washers do just fine, and in fact they do better than the fiber ones as you won't find yourself pulling off the road to re-tighten the bolts after the fiber ones take a set:
Takes about 500 miles; trip to the Lit Meet after the twin-plug build, pulling off 101N in the San Fernando Valley on return. They did not need it again, but then I switched to metal crush washers not long afterwards.
BTW, if you design to a generous diameter for sealing, you can use a "Dowty Washer" which captures an O-ring inside a metallic washer. The March F-1 used them in various locations, but both Zenith and Porsche were a bit more economical of sealing ring diameter.

[Martin Benade]

I'll stick with fiber, but its good to know that either is appropriate. My mind is made up already, don't confuse me with facts.

[David Green]

I had to have a helicoil installed in one Solex inlet and the banjo continued to have a slight leak despite trying various combinations of aluminum, copper and fiber washers. One day after warming it up I gave the banjo bolt a slight tug to stop the leak and it felt like it hit home. Turns out the way my machinist installed the helicoil the bolt bottomed out a few thousands short so it never crushed the washers. I filed the end of the bolt just until the washers sealed and problem solved. In my case the aluminum seem to seal the best.
David