C2 Fuel Tank Sending Unit O-Ring

[Donald H.]

This is probably on the TDB somewhere, But I couldn't find it.

I'm installing a new fuel tank on my 66 chassis and am ready to install the restored fuel sending unit.

The O-Ring has a small tab in one place on the inner side, is there a specific orientation for the O-Ring tab? I don't see anything obvious on the underside of the fuel sending unit.

Thanks,
Don

[Edward J.]

Re: C2 Fuel Tank Sending Unit O-Ring

Don, is it possible that it maybe used to keep the o-ring from moving during the sender install? maybe 180 degrees from the tab that align's sender unit onto tank.

[Joe L.]

Re: C2 Fuel Tank Sending Unit O-Ring

This is probably on the TDB somewhere, But I couldn't find it.

I'm installing a new fuel tank on my 66 chassis and am ready to install the restored fuel sending unit.

The O-Ring has a small tab in one place on the inner side, is there a specific orientation for the O-Ring tab? I don't see anything obvious on the underside of the fuel sending unit.

Thanks,
Don

Don-------


There's nothing on the sending unit. However, as I seem to recall, there's a "slot" for the tab on the fuel tank.

[Don H.]

Re: C2 Fuel Tank Sending Unit O-Ring

Yes there is a slot as Joe mentioned. (Just did mine this spring.) Don H.

[Donald H.]

Re: C2 Fuel Tank Sending Unit O-Ring

I'm installing a new Quanta reproduction tank and I don't see a slot on it. Maybe something missing on the reproduction!

[Wayne W.]

Re: C2 Fuel Tank Sending Unit O-Ring

There is a slot for the ground lug, but I don't rember anything for the rubber.

[Stephen L.]

Re: C2 Fuel Tank Sending Unit O-Ring

This is an original fuel tank flange and sending unit. Maybe this will help answer your question.

[John D.]

Re: C2 Fuel Tank Sending Unit O-Ring

I don't know the configuration of this o'ring. Not all o'rings are made the same. Would it be possible to install a viton o'ring instead of the original buna rubber one? That way ethanol wouldn't hurt it down the road.
Only problem is you would have to buy the o'ring in quantity.
Give me a pic and the dimensions and I will research it for you. John

[Gary B.]

Re: C2 Fuel Tank Sending Unit O-Ring

JD,

Here's a photo of a NOS GM o-ring. The OD is 2.375"; ID 1.875". So the "wire" diameter is 0.250".

Gary

GM NOS O-ring.jpg

[Wayne W.]

Re: C2 Fuel Tank Sending Unit O-Ring

I don't know the configuration of this o'ring. Not all o'rings are made the same. Would it be possible to install a viton o'ring instead of the original buna rubber one? That way ethanol wouldn't hurt it down the road.
Only problem is you would have to buy the o'ring in quantity.
Give me a pic and the dimensions and I will research it for you. John

The new replacements have an alcohol safe O ring, however it is slightly smaller in diameter than the originals, and I have had some leak.

[Donald H.]

Re: C2 Fuel Tank Sending Unit O-Ring

Here's a couple of pictures. The one on the left in the first picture is possibly of viton, it is brown in color. The one on the right is one I purchased advertised as a genuine GM. The brown one is 5.2mm in diameter/thickness and the GM one is 6mm. The second picture is with the brown one stacked on top of the GM black one.

Looks like the OD and ID of the brown one would fit, but I suspect there could be some leaking due to the thinner diameter/thickness.

I think I got the brown from John Wolf and Co with my restored original sending unit.

Don

[Joe L.]

Re: C2 Fuel Tank Sending Unit O-Ring

I don't know the configuration of this o'ring. Not all o'rings are made the same. Would it be possible to install a viton o'ring instead of the original buna rubber one? That way ethanol wouldn't hurt it down the road.
Only problem is you would have to buy the o'ring in quantity.
Give me a pic and the dimensions and I will research it for you. John

John------

I'm not sure if the GM rubber gasket is buna-N material, or not. However, buna-N is about as resistant to ethanol as it is to gasoline.

[John D.]

Re: C2 Fuel Tank Sending Unit O-Ring

John------

I'm not sure if the GM rubber gasket is buna-N material, or not. However, buna-N is about as resistant to ethanol as it is to gasoline.

Joe. I have done seminars titled, "The Evils of Ethanol" for the Pittsburgh chapter. In that seminar I bring buna rubber parts and viton rubber parts. I put both in various beakers of 10% ethanol. The buna rubber parts and Hoses swell up in short order.

You know friends I have been worried about this sending tank o'ring for years but never brought it up here.
Viton rubber comes in two colors. Brownish and satin black.
Wayne said he has issues with the undersize one.
Check with McMaster Carr on the viton o'ring. If the size you want is not in their catalog (on line) they can special order it for you. Don't plan on buying one though. But whatever and sale them to our friends here. Would be a good thing for someone to do.
Back to work, JD

[Gary B.]

Re: C2 Fuel Tank Sending Unit O-Ring

...
Check with McMaster Carr on the viton o'ring. If the size you want is not in their catalog (on line) they can special order it for you. Don't plan on buying one though. But whatever and sale them to our friends here. Would be a good thing for someone to do.
Back to work, JD

JD,

Sounds like an interesting hobby-business idea, but as they say on the Shark Tank, I'm out.

Gary

[Mike M.]

Re: C2 Fuel Tank Sending Unit O-Ring

i've always coated the GM o-rings( that came with nos tank sending units) with a liberal coat of silicone dielectric grease. have for years and haven't experience any o-ring failures. maybe the grease inhibits ethanol's adverse effects on the rubber. mike