Fittings

Fittings: the plumbing that ties your fuel, oil and coolant system together

Every custom or upgraded engine plumbing job lives or dies on its fittings. These are the threaded and welded connectors that join hose to hard line, adapt one thread standard to another, and give you leak-free seals at the fuel rail, oil cooler, catch can and coolant crossover. Get an AN hose end torqued onto braided line, weld a bung into a tank or tube, thread in a Y-block to split a feed, and you have a system that comes apart cleanly for service instead of a mess of hose clamps. The right fitting is what turns a pile of parts into a plumbing run that holds pressure.

What ThreePiece stocks

This category runs 634 products from 21 brands, with current in-stock prices from $20 to $264 (a range on what is here now, not a fixed quote). Vibrant is the deepest line at 409 items, followed by Fragola hose ends at 77 and Radium Engineering at 61, with DeatschWerks, Russell, Mishimoto, Turbosmart and Aeromotive rounding out the shelf. Example parts show the spread: a Vibrant stainless weld fitting for 5in OD tubing at the top end, a Vibrant -10AN quick release with Viton seal, a DeatschWerks 6AN dry break quick disconnect, a Mishimoto 3/4in one-way check valve fitting, and an Aeromotive AN-06 Y-block.

How to choose

Start with the connection type. Hose ends like the Fragola 90-degree Pro-Flow attach to braided line by AN size, so match the dash number to your hose and rail. Weld fittings and bungs, like the Vibrant stainless piece, are for permanent joints into tanks and tubing, sized to the tube OD. Quick releases and dry breaks cost more but let you disconnect a line without draining the system, useful on removable panels and tank runs. Y-blocks split one feed into two. Aluminum keeps weight and price down; stainless suits high-pressure or heat. Angle matters too, buy the elbow that lets your hose exit cleanly instead of kinking a straight fitting into place.

What else you need with it

Fittings rarely go in alone. Plan the whole run: pair them with Adapters when you cross thread standards, and feed them from Fuel Pumps and Fuel Injectors on the fuel side. Coolant plumbing often ties into Radiators, and any teardown to route new lines is the time to check Gasket Kits. Browse the full Engine Components section for the rest of the build.

Fitment and ordering

Only 4 products here carry vehicle fitment data, with sampled coverage touching makes like Nissan, Subaru, Cummins and Dodge across model years 1989 to 2023, including the Nissan 240SX, Subaru EJ and Cummins 6.7L. Most fittings are sized by AN and thread, not by vehicle, so confirm the size before ordering. Not sure? Call fitment help at 813-535-5801 or reach us through contact us. Every order ships free, and Affirm and Katapult financing is available on the financing page.

Fittings: the plumbing that ties your fuel, oil and coolant system together

Every custom or upgraded engine plumbing job lives or dies on its fittings. These are the threaded and welded connectors that join hose to hard line, adapt one thread standard to another, and give you leak-free seals at the fuel rail, oil cooler, catch can and coolant crossover. Get an AN hose end torqued onto braided line, weld a bung into a tank or tube, thread in a Y-block to split a feed, and you have a system that comes apart cleanly for service instead of a mess of hose clamps. The right fitting is what turns a pile of parts into a plumbing run that holds pressure.

What ThreePiece stocks

This category runs 634 products from 21 brands, with current in-stock prices from $20 to $264 (a range on what is here now, not a fixed quote). Vibrant is the deepest line at 409 items, followed by Fragola hose ends at 77 and Radium Engineering at 61, with DeatschWerks, Russell, Mishimoto, Turbosmart and Aeromotive rounding out the shelf. Example parts show the spread: a Vibrant stainless weld fitting for 5in OD tubing at the top end, a Vibrant -10AN quick release with Viton seal, a DeatschWerks 6AN dry break quick disconnect, a Mishimoto 3/4in one-way check valve fitting, and an Aeromotive AN-06 Y-block.

How to choose

Start with the connection type. Hose ends like the Fragola 90-degree Pro-Flow attach to braided line by AN size, so match the dash number to your hose and rail. Weld fittings and bungs, like the Vibrant stainless piece, are for permanent joints into tanks and tubing, sized to the tube OD. Quick releases and dry breaks cost more but let you disconnect a line without draining the system, useful on removable panels and tank runs. Y-blocks split one feed into two. Aluminum keeps weight and price down; stainless suits high-pressure or heat. Angle matters too, buy the elbow that lets your hose exit cleanly instead of kinking a straight fitting into place.

What else you need with it

Fittings rarely go in alone. Plan the whole run: pair them with Adapters when you cross thread standards, and feed them from Fuel Pumps and Fuel Injectors on the fuel side. Coolant plumbing often ties into Radiators, and any teardown to route new lines is the time to check Gasket Kits. Browse the full Engine Components section for the rest of the build.

Fitment and ordering

Only 4 products here carry vehicle fitment data, with sampled coverage touching makes like Nissan, Subaru, Cummins and Dodge across model years 1989 to 2023, including the Nissan 240SX, Subaru EJ and Cummins 6.7L. Most fittings are sized by AN and thread, not by vehicle, so confirm the size before ordering. Not sure? Call fitment help at 813-535-5801 or reach us through contact us. Every order ships free, and Affirm and Katapult financing is available on the financing page.