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Lycoming O320 H2AD Camshaft Inspection

suggestion from one of our contributors

worn camshaft lobe. Notice how top of lobe shows contact from one end to the other. Normally wear doesn't extend to the edges of the lobe.

Despite a wealth of service bulletins and AD's this engine continues to cause concern, whereas the simplicity of inspection in respect of the cam followers and camshaft actually makes it possible to improve reliability over engines which do not enjoy barrel tappets.

My suggestion is as follows:- Each 500 hours, remove rocker covers and strip out rockers and push rods being sure to account for every one of the shims under the rocker pivots and keeping the rods with their respective valves. Remove all of the tappets and carefully inspect the faces for any sign of spalling or chipped edges. Inspect the camshaft lobes with powerful illumination for any signs of broken edges, waviness or uneven wear. Followers which fail inspection or even look suspicious should be discarded and renewed BUT make sure to repeat the inspection of the camshaft lobe of the rejected tappet and measure the valve lift. Lycoming do not publish the valve lift figures but I can tell you that it is!
Should be 0.30296\" plus or minus 0.002\"

That's 303 thou of an inch. Those cams that operate two valves should have equal readings on each side or course. If you have any more that ten thou wear on any one lobe my recommendation is to scrap the camshaft. It isn't worth the risk. When those lobes break up they break up fast and within an hour you\'ll have so much metal in the oil pan that you can\'t get the suction screen out. Of course you won\'t need me to tell you that for the O-320 H2AD a suction screen inspection at EVERY oil change might save your life.

Further information on inspecting camshaft lobes

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