AN to INV Fittings

INV means inverted flare. It describes the flare seat used on one side of the adapter, not a separate automotive thread standard or AN size. An AN to inverted flare adapter connects a compatible AN fitting to a component or hard line that uses the specified inverted flare connection. Because inverted flare fittings are available with different inch and metric threads, “INV” alone is not enough to select a part. You must also confirm the full thread size, pitch, connection gender, line diameter and flare-seat geometry.

Select a thread adapter using five checks: the application system, compatible fluid, AN size, inverted flare thread and flare-seat type. For the AN side, confirm the listed size and whether the required connection is male or female. For the other side, verify the complete thread specification, such as 3/8-24, 1/2-20, 5/8-18, M10x1.0 or M10x1.25. Then compare the fitting seat with the existing port or hard line. Vehicle make and model alone are not enough because thread and flare configurations can vary by component.

No. 3AN and 3/8-24 inverted flare connections may share a 3/8-24 thread designation, but they do not use the same sealing geometry. A 3AN connection seals on a 37 degree AN flare, while a typical SAE inverted flare connection seals against a matching inverted flare seat. The connection may begin to thread together even when the seats are incompatible. Never use thread engagement alone to confirm fitment. Check the flare angle, seat shape, connection gender and intended line size before installation.

Only when the individual product specifications identify the intended system and compatible media. This Evil Energy collection contains some fuel system fittings for confirmed fuel or cooler applications, along with stainless-steel brake line adapters intended for compatible brake or clutch hydraulic circuits. A fitting listed for a fuel or cooler system should not automatically be treated as a brake fitting, and a brake adapter should not automatically be used in a fuel system. Match the product’s material, pressure specification, compatible fluid, thread and flare seat to the intended installation.

Normally, no. AN flare and inverted flare connections seal metal to metal at their mating seats, rather than at the threads. PTFE tape or thread sealant on a flare connection can interfere with full seat contact and may contaminate the fluid circuit. Keep the sealing cones and seats clean and free from scratches. Do not add lubricant or sealing compounds unless the specific product or component manufacturer explicitly requires them. After installation, inspect the connection and perform the appropriate system leak check before returning the vehicle to service.