Restricted Exhaust System

A restricted or blocked exhaust system usually results in loss of power or popping through carburetor. Ensure that the condition is not caused by timing or ignition problems before testing for restricted exhaust system.

1. Visually inspect the complete exhaust system. If exhaust system is collapsed, replace damaged components. If exhaust system is okay, connect a vacuum gauge to intake manifold source. Connect tachometer.
2. Start engine and with transmission in Neutral, gradually increase engine speed to 2000 RPM. Check manifold vacuum reading on gauge. If manifold vacuum is greater than 16 in. Hg, exhaust system is okay.
3. If manifold vacuum is less than 16 in. Hg, turn engine off and disconnect exhaust from exhaust manifold(s). Repeat step 2). If manifold vacuum is less than 16 in. Hg, remove exhaust manifold(s).
4. Check ports for casting flash by dropping a length of chain into each port. DO NOT use a wire or light to check ports, restriction may be small enough to cause excessive backpressure at high RPM.
5. Check for restriction. If restriction is present, remove casting flash. If flash cannot be removed, replace exhaust manifold. If no restriction is present, exhaust system is okay.
6. If manifold vacuum is greater than 16 in. Hg, reconnect exhaust system to manifold(s). Disconnect muffler(s). Repeat step 2).
7. If manifold vacuum is less than 16 in. Hg, replace catalytic converter and check to ensure converter debris has not entered muffler. If manifold vacuum is greater than 16 in. Hg, replace muffler.