Specialized Fittings & Accessories

These three fitting families solve different problems, and mixing them up is the fastest way to end up with a leak. AN fittings seal on a 37 degree flare and are used almost anywhere braided or PTFE line connects to a fuel rail, pump, or regulator with a straight O ring port. NPT fittings use tapered threads and show up on filters, senders, and pressure ports that were machined for pipe thread, and they are also the one place on a fuel system where thread sealant actually belongs. Hardline compression adapters cover the transition point where flexible hose ends and rigid aluminum or steel line begins, most often on the run between a pump or filter and the tank. Before ordering, check the port the fitting threads into rather than the hose running to it, since the port is what actually sets the thread standard needed. A side by side breakdown of each type is in the fitting selection guide.

For most street and daily driven builds, anodized aluminum fittings are the standard choice. They are lighter, cost less, and hold up well as long as the anodized finish stays intact. Stainless steel is worth the upgrade for builds that spend time in salt belt states, marine use, or high heat areas near the exhaust, since it resists corrosion in conditions that will eventually pit or discolor aluminum. One point worth flagging directly: aluminum fittings crack rather than bend if they are over torqued, so a wrench and a bit of restraint matter more than the material choice for most leak complaints.

Aluminum and stainless AN adapters are compatible with gasoline, diesel, and E85, but the hose and seal material connected to them is what actually determines E85 safety, not the fitting metal alone. Standard rubber lined hose is not rated for E85 or methanol, so any adapter feeding one of those fuels should be paired with PTFE lined hose or hardline, not rubber. On the pressure side, fittings in this collection are individually rated as high as 4000 PSI depending on the design, which covers naturally aspirated, forced induction, and most return style EFI setups.

Yes, and that is the entire point of this collection. Every fitting here, from block off plugs to Y block splitters to weld on bungs, is sold individually rather than bundled into a fixed kit. Complex routing, tight engine bays, and non standard ports tend to reveal a missing connector only after the rest of the system is already installed, and there is no need to buy an entire new fitting kit to source that one piece.

Most leaks trace back to one of three mistakes. First, thread sealant on an AN fitting flare, which should never be used since AN fittings seal on the flare face rather than the threads, while sealant is required on tapered NPT fittings. Second, over tightening: aluminum fittings should be snugged hand tight and then brought home with a modest additional turn of the wrench, not cranked down, since aluminum tends to crack under excess torque rather than seal any tighter. Third, unsupported components: a fuel pressure regulator, filter, or fitting cluster hanging on hose alone puts constant strain on every connection and is a common cause of slow leaks over time, so anything with real weight should be clamped or bracketed to the chassis. Checking the assembly at low pressure before it goes back on the vehicle catches most of these issues before they reach the road.