Boschma's Exhaust Evac System

Old-school race-engine crankcase ventilation, powered by exhaust flow. The Boschma's Speed Shop Exhaust Evac System, part number evac01, fits all model-year Ford Mustangs and is for building an exhaust-driven crankcase evacuation setup.

What does an exhaust evac system do?

Combustion gases that get past the piston rings, known as blow-by, enter the crankcase and can build pressure. An exhaust evac setup uses exhaust flowing past correctly positioned pickup tubes to create suction, helping draw crankcase vapors out through hoses connected to suitable valve-cover breathers or evacuation fittings.

Why racers use it

Helping control crankcase pressure can reduce the tendency for oil to push past seals and gaskets. Under suitable conditions, crankcase vacuum can also support ring sealing and reduce pumping losses. Results depend on the engine, exhaust design, blow-by, and installation; horsepower gains or a specific vacuum level are not guaranteed.

The old-school approach

This is the traditional header-evac approach used on drag-racing engines, particularly with low-restriction exhausts or open headers. Unlike a belt-driven vacuum pump, it relies on exhaust flow to generate suction. Pickup placement and angle are important, and suitable one-way check valves help prevent exhaust pressure from flowing back toward the engine. Mufflers and exhaust backpressure can reduce effectiveness or make a setup unsuitable.

Pictured components

The photo shows two metal evacuation tubes, threaded adapters and nuts, two black couplers with clamps, two angled hose-fitting assemblies, and braided hose.

Mustang fitment and installation

Fits all model-year Ford Mustangs. Installation requirements vary with the engine and exhaust configuration; this does not mean a direct bolt-on installation with every factory exhaust. Confirm connection sizes, hose length, valve-cover connections, and check-valve requirements for your build. Exhaust fabrication may be required. Have a qualified installer assess the setup and verify crankcase vacuum after installation. This system does not repair worn rings or excessive blow-by.

Part number: evac01. Free standard shipping on this item. Contact Boschma's Speed Shop for help matching the system to your build.