Universal 6AN Fuel Tank Return Line Collapsible Bung Kit (9/16"-18 Thread / Drill-In No-Weld Installation / Billet Aluminum)

Add a return line port to virtually any fuel tank without welding using this premium collapsible bung kit, precision CNC-machined from 6061-T6 aircraft-grade aluminum for permanent durability and reliable fuel system sealing. Adding a fuel return line to a tank is a common requirement for engine swap projects, EFI conversions on carbureted vehicles, fuel system upgrades, and dedicated race fuel cell installations — but traditional welding installation requires removing the fuel tank, draining residual fuel, and exposing the tank to welding heat near explosive fuel vapors. This collapsible bung kit eliminates the welding requirement entirely with an innovative drill-and-collapse installation that creates a secure, leak-free threaded fitting in just minutes. Simply drill a 1/2" hole, insert the collapsible bung, and tighten the center bolt — the bung collapses inside the tank, pressing against the interior tank wall to create a permanent sealed connection point. Includes a 9/16"-18 thread to 6AN fitting for direct integration with standard performance fuel system plumbing.

Features:

• No-weld installation – allows you to add a threaded fuel line bung to virtually any fuel tank without welding, dramatically reducing safety risk and installation complexity
• Simple drill-and-collapse design – drill a 1/2" hole, insert the bung, and tighten the center bolt to collapse the bung against the inside of the tank for permanent secure mounting
• Premium 6061-T6 billet aluminum construction – CNC machined from aircraft-grade aluminum for exceptional strength and durability
• Anodized surface finish – delivers superior rust resistance and corrosion protection against fuel exposure
• O-ring included – prevents leakage and ensures fuel-tight sealing at the bung-to-tank interface
• Compatible with tank wall thickness up to 1/4" – works with virtually any automotive fuel tank, fuel cell, or aftermarket tank
• 9/16"-18 thread to 6AN fitting – direct compatibility with standard performance fuel system plumbing
• Universal application – fits any fuel tank application requiring an additional return line port

Specifications:

• Condition: 100% Brand New
• Type: Universal Fuel Tank Return Line Collapsible Bung Kit
• Material: 6061-T6 Aircraft-Grade Billet Aluminium
• Construction: CNC Machined
• Surface Finish: Anodized
• Thread Size: 9/16"-18
• Fitting Size: 6AN
• Hole Size Required: 1/2"
• Maximum Tank Wall Thickness: 1/4"
• Sealing: O-Ring (Included)
• Item Weight: 0.07 kg
• Quantity: 1 complete bung kit per pack
• Position: Fuel Tank Return Line Port
• Purpose: Custom Fuel System Installation / EFI Conversion / Engine Swap Component

Fitment:

• Universal application – compatible with virtually any automotive fuel tank, aftermarket fuel cell, or steel/aluminum tank requiring a return line port
• Compatible with tank wall thickness up to 1/4" (6.35mm)
• Suitable for engine swap projects, EFI conversions, carb-to-EFI upgrades, and dedicated race fuel system installations
• Compatible with standard 6AN performance fuel line plumbing

Contents:

• 1x Universal Fuel Tank Return Line Bung Kit (Collapsible Bung + 9/16"-18 to 6AN Fitting + O-Ring + Mounting Hardware)

Benefits:

• Eliminates the welding requirement traditionally needed to add fuel tank ports – significantly safer than welding near fuel vapors and dramatically simpler installation
• Enables EFI conversion on carbureted vehicles – many EFI systems require a return line, and this kit provides a clean way to add the return port to existing tanks
• Critical component for engine swap projects – allows the addition of return-style fuel systems to vehicles originally equipped with return-less or carbureted fuel systems
• 6061-T6 aircraft-grade billet aluminum construction provides permanent dimensional stability – will not corrode, crack, or fail when properly installed
• Anodized finish protects against fuel exposure, weather, and underbody conditions for the lifetime of the installation
• O-ring sealing ensures permanent leak-free operation – critical for fuel system safety and avoiding costly fuel leak issues
• Compact design enables installation in tight tank locations where welding would be impractical or impossible
• Universal compatibility makes this versatile for any fuel system project across virtually any vehicle platform
• Significant cost and time savings compared to professional welded bung installation – this kit can be installed in minutes by any DIY builder

Important Use-Case Notes:

• Universal application: This bung kit works with virtually any fuel tank, but installation location should be carefully selected to ensure proper return line submersion and tank function
• Tank wall thickness limit: Compatible with tanks up to 1/4" wall thickness – verify your tank wall thickness before ordering
• Tank material compatibility: Works with steel, aluminum, and most plastic fuel tanks – verify compatibility with your specific tank material
• Required tools: Installation requires a 1/2" drill bit, drill, and torque wrench or power tool capable of 60 Nm torque

Installation Notes:

• Safety first: Drain the fuel tank completely or remove residual fuel before drilling – fuel vapors are explosive and any sparks during drilling can cause catastrophic ignition
• Proper safety equipment: Use eye protection, work in a well-ventilated area, and have appropriate fire suppression equipment readily available during installation
• Tank position selection: Choose the bung location carefully – the return line outlet should be positioned to ensure proper return line submersion under typical fuel levels and to avoid interference with the tank's fuel pickup or sending unit
• Mark and drill a 1/2" hole at the selected installation location – use a step bit or precise hole saw for clean cutting
• Deburr the hole edges thoroughly before installing the bung – sharp edges can damage the O-ring during installation
• Insert the bung through the hole from outside the tank with the O-ring properly seated
• Position the bung's collapse mechanism inside the tank – verify proper orientation before tightening
• Tighten the center bolt to a torque value of 60 Nm using a torque wrench or power tool – this collapses the bung internally to create a sealed connection
• Verify the bung is firmly seated and pressed against the inside tank wall after tightening – it should not rotate or move when tightening is complete
• Connect 6AN fuel line to the threaded fitting using appropriate AN-grade fuel line, hose ends, and clamps
• Test for leaks before refilling the tank with fuel – pressurize the tank with air or use a leak-down test method
• Refill the tank only after verifying leak-free operation
• Inspect the installation periodically for any signs of leakage or loosening
• Professional installation strongly recommended for first-time installers or for installations on plastic fuel tanks
• If unsure about installation procedure, tank compatibility, or safety considerations, consult a qualified fuel system specialist before proceeding

Warranty:

• 12-month standard warranty from date of purchase
• Contact our support team for assistance with any issues