Engine Breather Filters

Engine Breather Filters

Engine breather filters are vented filtration caps and inline filter assemblies that allow crankcase pressure to vent safely to atmosphere without releasing raw oil vapor, reducing the internal pressure buildup that can push past valve cover seals, rear main seals, and PCV grommets in high-output and modified engines. Unlike a standard PCV system that routes crankcase gases back into the intake manifold, an open breather filter vents directly to air, making it the preferred choice on dedicated track cars, drag builds, and any engine running so much blowby that the factory PCV system cannot handle the volume without saturating the intake with oil mist. Performance engines that produce significantly more blowby than stock through increased displacement, high-lift camshafts, or forced induction benefit most from breather filter upgrades that vent excess crankcase pressure without contaminating the intake charge. Proper crankcase ventilation reduces oil consumption, keeps the intake tract cleaner, and extends oil change intervals on high-mileage performance applications.

Popular Upgrades

Popular engine breather filter products include K&N breather caps in both push-in and threaded configurations that fit standard 1-inch, 1.25-inch, and 1.5-inch valve cover bung diameters, Moroso breather filter setups for oval track and drag applications that include a remote overflow canister to capture liquid oil before it exits the breather, and Earl's and Vibrant Performance inline crankcase breather filters for custom fabricated ventilation setups on turbocharged and supercharged engines. Oil catch can systems from Billet Technology and MightyMouse that incorporate a breather filter at the vent outlet are a popular combined solution for Hellcat, Trackhawk, and LS-based boosted builds where both PCV routing and crankcase venting require management.

Performance and Handling

A well-designed engine breather filter system prevents the vacuum and pressure cycles in the crankcase from forcing oil past gaskets and seals, which is the primary cause of the oil consumption issues that appear on modified engines shortly after performance upgrades increase blowby beyond the factory PCV system's design capacity. On turbocharged engines, positive crankcase pressure that is not managed by adequate venting can also pressurize the oil return line from the turbocharger, causing oil to pool in the center housing and be pulled into the compressor side on boost. Matching breather filter flow capacity to the actual blowby volume of the engine, rather than using the smallest available unit, is the most important sizing decision for any crankcase ventilation upgrade.

What size breather filter do I need?

Breather filter sizing depends on the valve cover bung diameter and the expected blowby volume, with most V8 street engines being adequately served by a K&N 62-1010 or equivalent 1.25-inch push-in breather cap on each valve cover. High-output engines above 600 horsepower, forced-induction builds, and engines with worn piston rings generating excessive blowby require larger flow-capacity filters or remote breather tank setups that can accommodate higher gas flow rates without pushing back-pressure into the crankcase. Measure the valve cover bung diameter before ordering to confirm whether a push-in or threaded breather is required.

Can I use a breather filter instead of a PCV valve?

Open breather filters vent to atmosphere rather than routing crankcase gases back into the intake, which means they are not emissions-compliant replacements for a PCV system on street-registered vehicles in most states. For dedicated race cars and track builds that operate under competition-only regulations, an open breather setup is acceptable and often preferred for its simplicity and reduced risk of oil contaminating the intake. Street builds that want cleaner crankcase ventilation should use a catch can system that routes gases back into the intake after separating out the oil, maintaining emissions compliance while improving over the factory PCV routing.

Why These Parts Fit Right

Breather filters in this collection are listed by bung diameter, thread pitch, and mounting type so you can confirm the correct fit for your valve cover or catch can outlet before ordering. Product pages include flow capacity data and application notes for common valve cover configurations on domestic V8, LS, HEMI, and import performance platforms. Fast shipping and expert support are available for any crankcase ventilation fitment question.

Pair your breather filter upgrade with a catch can from our exhaust collection, improve chassis stability with upgrades from our suspension catalog, and maximize induction airflow with parts from our air intake systems collection.