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Horror Stories

Mistimed Camshaft

 

 

This happened on a 270 bore medium speed engine (built under licence in China) driving an alternator which had only done a thousand hours from new. A knocking noise severe vibration from the turbocharger, and a high oil mist alarm caused the engine to shut down.

On opening up for inspection the badly damaged piston with a hole punched through it and the remains of two valve heads were found.

 

 

The turbocharger nozzle ring and blading were also badly damaged by the debris which passed through the turbocharger.

 

Inspection of other units showed that all the piston crowns had been damaged where they were hitting the valves. When the rockers were stripped down some of the tappets were found to be smashed.

 

 

On this engine there are two camshafts; one for the inlet and exhaust valves and one for the fuel pumps. The cause was found to be mistiming of the valve camshaft by one tooth, which resulted in a rebuild of the engine.

 

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