47-55.1 SBC 350 leaking fuel pump line - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dsraven · 11-16-2018, 03:38 PM

is the fitting on the end of the tank bib threaded onto the bib or is that a compression fitting?
here is a wikipedia link for AN fitting sizes and how it all works
https://en.wikipedia.org/wiki/AN_thread

9/16-18 would be the threaded adapter part and usually has an O ring on it opposite the AN end. the AN fitting is usually classified as a number relating to 1/16 of an inch, so a #6 AN would be 6 x 1/16 which breaks down to 3/8. that is even a bit hard to understand because the different AN fittings can be classified as per wall thickness of the tubing it is used for, not like a bolt size.
I would have to say the fitting coming off the pump is likely a 1/4" npt (red arrow)

https://www.speedwaymotors.com/Small...BoCtfsQAvD_BwE

and the hose connected to that looks like a 6AN fitting (yellow arrow) but you may be able to check that by the wrench size (not always).

https://www.dragstuff.com/techarticl...nce-Chart.html

when you get that end apart I would see what size of hole is in the actual fittings where the fuel goes through just to ensure you will have ample fuel flow.

the white arrow is a bit of a guess because there is not good pic that shows the whole thing and the description is kinda off compared to the pic. maybe the PO threaded the inside of the 6ANx 9/16-18 adapter fitting so the tank bib tube would screw inside and the AN end of the fitting would connect to the hose. that's why I asked if it is a compression fitting onto the bib tube or if the bib is screwed into the end of the adapter fitting.

https://www.speedwaymotors.com/Hydra...ht,342357.html

either way, the bib tube needs to be supported for the added weight that the new hose and fittings will add. work fatigue on that bib, from vibration, could cause stress cracks and the bib could break off and burn your truck down if it doesn't have good support. especially if you add a petcock. that system has got to weigh more than the simple rubber hose that went to the steel line on the original frame, even if it had an inline fuel filter attached.
anyway, hope that helps and not confuses you

11-16-2018, 03:38 PM	#12
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 9,047	Re: SBC 350 leaking fuel pump line is the fitting on the end of the tank bib threaded onto the bib or is that a compression fitting? here is a wikipedia link for AN fitting sizes and how it all works https://en.wikipedia.org/wiki/AN_thread 9/16-18 would be the threaded adapter part and usually has an O ring on it opposite the AN end. the AN fitting is usually classified as a number relating to 1/16 of an inch, so a #6 AN would be 6 x 1/16 which breaks down to 3/8. that is even a bit hard to understand because the different AN fittings can be classified as per wall thickness of the tubing it is used for, not like a bolt size. I would have to say the fitting coming off the pump is likely a 1/4" npt (red arrow) https://www.speedwaymotors.com/Small...BoCtfsQAvD_BwE and the hose connected to that looks like a 6AN fitting (yellow arrow) but you may be able to check that by the wrench size (not always). https://www.dragstuff.com/techarticl...nce-Chart.html when you get that end apart I would see what size of hole is in the actual fittings where the fuel goes through just to ensure you will have ample fuel flow. the white arrow is a bit of a guess because there is not good pic that shows the whole thing and the description is kinda off compared to the pic. maybe the PO threaded the inside of the 6ANx 9/16-18 adapter fitting so the tank bib tube would screw inside and the AN end of the fitting would connect to the hose. that's why I asked if it is a compression fitting onto the bib tube or if the bib is screwed into the end of the adapter fitting. https://www.speedwaymotors.com/Hydra...ht,342357.html either way, the bib tube needs to be supported for the added weight that the new hose and fittings will add. work fatigue on that bib, from vibration, could cause stress cracks and the bib could break off and burn your truck down if it doesn't have good support. especially if you add a petcock. that system has got to weigh more than the simple rubber hose that went to the steel line on the original frame, even if it had an inline fuel filter attached. anyway, hope that helps and not confuses you



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