Can anybody tell me what size fitting I need to connect to the stock fuel sending unit? Trying to go from that to -6 an fuel line. I was told RUS-640830 would work, but it doesn't. It's about two sizes too small. I looked for an 18 mm fitting but couldn't find one.

 

I just did this. You can use a russel tube and nut but mine always leaked and I switched to a swaglok fitting. 3/8 compression for tube and 6 an male end to attach to my teflon braided lines. No flaring with the swaglock. Here is the part I used:

http://www.swagelok.com/search/find_products_home.aspx?part=SS-600-6-6AN

They have local dealers all around the country. Hope that helps.

 

9894DBHERL (1) - 14mm to -6AN
9894DBJERL (1) - 16mm to -6AN

Those are the two I used to connect my stock hardline fittings to -6AN. I have a TBI car, not sure if tuned port or carb have different fittings, but mine were definitely 16/14.

 

I dont think the factory lines are mm. They are 3/8 feed 5/16 return outside diameter. The fitting I posted fits. Google swaglock. Alot of forum car guys use them. I usd the tube nut adapters from russel. Have to be careful. The factory feed lines may be seamed. A flare on a seamed tube never seals correctly . I had to use conical washers from earls to seal the end. Didnt like that setup. This ones compression, the swaglock. Cut straight, debur, seat tube, turn a turn and a 1/4 from finger tight. Done. Goodluck.

 

I ended up using a fitting I had from my HSR fuel line setup. The hard line coming off of the sending unit has the same fitting as the feed line up by the brake booster.

 

At the engine bay side they are definately 16/14 mm fittings. Lines may be 3/8 and 5/16 diameter but those part numbers are whats needed for AN lines at engine bay side

Havent looked at stock thirdgen tank side to AN. On 4th gens the pump assembly discharges out the plastic ports into rubber line. They make disconnect type fittings for converting those to AN braided line. I imagine thirdgen tanks could do similar but need to check

 

The fittings you need can be found in a tbi throttlebody....