We recently launched some new fuel fitting parts so you can make 5/16in fuel lines for Stromberg 97s. While the stock early Ford 1/4in OD hard lines are great-looking for a typical flathead motor, many people like the thicker lines for Chevys and other applications. This includes us, of course, as our recently launched 9146-BIG 3-into-1 fuel line uses 5/16in OD stainless hard line. And more than that, all our forthcoming new Stromberg BIG 97s are 5/16in hard line compatible. You can see in these pictures how the BIG S-jet seats the 5/16in line and what happens when you try it in the regular S-jet – it leaves no seat for the ferrule. Click to enlarge.

Today we got a tech enquiry from Shane Dale in Australia that covers this very question, so we thought we’d share it here:

Hello, I have three new 97’s that I purchased in 2011 and am finally getting around to fitting up. I will be bending my own 5/16 OD hard line and was wondering what size fitting will screw into the carb? I purchased three 9180K’s and started hand screwing them but stopped quickly as it went tight.

Hi Shane, A couple of issues here. Firstly, 9180K is our 1/4NPT hard line adapter so the tapered NPT thread won’t fit into the S-jet, which is 1/2in UNF – that’s why it went tight. And as you worked out, regular Stromberg 97 inlet valves (needle & seats) were designed with a 1/4in pocket to take the line and the angled seat is positioned so the brass ferrule can compress properly to seal on the 1/4 pipe. If you put 5/16in line in, it doesn’t sit in the hole properly and covers most of the angled ferrule sealing surface. The good news is, we recently developed a new S-jet inlet valve for our 97s specifically for 5/16th line, and we also just launched a pack of compatible ‘Ford Nut’ style compression fittings for them. You need 3 x 9564K-BIG (the S-jet inlet valve) and just one pack (3 nuts and 3 ferrules in a pack) of 9081K-BIG (the Ford Nut for 5/16th line).

All the best, Stromberg Tech.