Filter Accessories

Filter accessories are the parts around an air filter: pre-filter wraps, top and base plates, velocity stacks, adapters, gaskets and hoses. The category also holds oil catch cans and weld-on fittings, for building, adapting or protecting an intake rather than replacing the filter itself.

A wrap is a coarse outer sleeve that stops larger particles and road dirt before they reach the main element. It stretches the interval between cleanings on dusty events. A soaked or clogged wrap restricts the airflow, though, so it needs cleaning in its own right.

Stacks and air horns give a carburettor or throttle body a rounded entry, which reduces the losses of a sharp-edged inlet. Their length also shifts where in the rev range the intake pulses help cylinder filling. Catch cans sit in the crankcase ventilation line and separate oil mist from the blow-by gas, keeping much of it off the intake tract and valves.

What to look for:

• Wraps: each is cut for a particular filter, and many carry that filter’s part number plus a suffix, so match the two. Foam wraps are listed too.
• Plates and tops: top plates, top and base plates, and top filter assemblies that let a round housing draw air through its lid as well. Some titles give a size, such as a 16 inch top plate.
• Stacks and air horns: velocity stack assemblies and short stub stacks for carburettor and throttle body entries.
• Adapters and seals: weld-on and rubber adapters, a weld-on boss for an air mass sensor, chloroprene rubber gaskets and rubber hoses.
• Catch cans: oil separators made for a particular engine, so start from the engine named in the title.

Depending on the country, intake and breather changes can need approval for road use, so check the rules where the car is registered. Weld fittings to a pipe before final assembly, then clear out all spatter and swarf. Place an air mass sensor boss in a straight section, away from bends. Empty a catch can at each service, more often on track, and replace gaskets that have hardened.