Radium 6AN ORB Bulkhead with 8.5mm Barb for Fuel Surge Tanks

Radium Engineering 6AN ORB Bulkhead with 8.5mm Barb to 6AN Male - Part #20-0170

This is the fitting that carries fuel through the lid of a Radium surge tank: a 6AN ORB threaded bulkhead with an 8.5mm hose barb on the tank side and a 6AN male flare on the outside. Radium has used it on its fuel surge tanks since 2014, and it's the part you order when you're adding a port, replacing one that got damaged, or plumbing a pump outlet through the lid on a custom tank with a 9/16-18 ORB hole.

What It Is and Why It Works

The outside of the fitting is a standard 6AN male flare for a hose end. The bulkhead threads into a 6AN ORB port (9/16-18 with an SAE chamfer) and seals on a preassembled Viton O-ring, which holds up to gasoline, E85, and methanol without swelling. Inside the tank, the 8.5mm barb takes 5/16 inch submersible fuel hose from the pump outlet, clamped, which is how every in-tank pump in a Radium FST connects to its port. The fitting is anodized aluminum, bright-dipped green to match Radium's surge tank hardware, and because it's a bulkhead rather than a tee, the pump outlet, the lid, and the external line become one sealed path with no fuel exposed to the tank interior.

Specs

Fitment

Not vehicle-specific. It will not seal in a plain tapped 9/16-18 hole without the chamfer, and it is not an NPT fitting.

What to Know Before You Buy

Use submersible-rated hose on the barb side; standard fuel hose is only rated for fuel on the inside, and inside a surge tank it's soaking in it. Lube the O-ring with a little oil before you thread it in and snug it by hand plus a quarter turn; ORB seals on the O-ring, and overtightening just squashes it. If you're replacing one on an existing Radium FST, the lid port is already chamfered. If you're drilling your own, the ORB port needs the spot face and chamfer, not just a tapped hole, or the O-ring extrudes. One per port; a typical surge tank lid uses several.