Muffler and Manifold Systems

Explosions in the muffler can be the result of intermittent ignition, throttle open and after-burning in the muffler due to lean gasoline mixture. Muffler explosions can occur if the ignition is turned on after the engine is cranked. The cure is to turn on the ignition first. If slight muffler explosions are heard when running downhill with the car in gear, ignition on and the throttle closed, see that the gas mixture is not too lean and that the spark is advanced all the way. Some causes of backfire are cold engine, spark retarded, mixture too lean, dirt in the carburetor, leaking through the intake valve, excessive clearance on the exhaust valves. The lack of sufficient fuel can create overheating of the exhaust manifold, which in turn creates popping noises. Clean out the fuel lines and adjust the carburetor for a possible cure. Symptoms of a leaky manifold are rough idling and poor performance. You can place a few drops of oil around the leaky gasket under the manifold. If the oil is sucked into the manifold and the engine changes in its idle, you could have an air leak at that point. If so, replace the gasket, but make sure the mounting surface is not too badly warped. The clamps holding the muffler to the exhaust muffler can let go with a bang! Don’t forget to check the muffler clamps often for looseness. When you tighten the nuts holding the exhaust and intake manifold in place, be sure to pull the nuts evenly, tightening each a little at a time. This procedure will prevent leaks and prevent the manifold from cracking which sometimes happens. Lastly, the smoke coming out of your tailpipe is telltale. Too much fuel or too little air creates black smoke to trail from the tailpipe. Excessive oil burning causes blue smoke. White smoke is caused by moisture and can be caused by head gasket problems.

This tech tip was originally printed in the Mar/Apr. 2000 “A” Quail Call.

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