Expert: Stephen Sokol Date: 3/22/2007 Subject: noise on my alfa 156
Question QUESTION: hi i have just rebuilt my top end after the cam belt snapped on my alfa 156 i have reground all valves put it all back together and now i am getting a noise when the engine is warm and doing between 2500 and 4500 rpm it disappers after 4500 but when i turn the engine off then back on again it does not do it straight away
ANSWER: It is a mistake to grind bent valves. It is also not a good idea to regrind modern valves. Take it apart, replace the 6 or 7 valves that bent (go ahead, replace all of them). But, first,carefully check the seats for integrity. Also, smooth any sharp impressions in the pistons.
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QUESTION: i did replace all valves and valve seals infact i had a complete top end gasket and seal set and there are no sharp edges the noise seems to be coming from below the inlet mainifold and sounds like a dry bearing would, but that would sound all the time or would it. the engine apart from the noise between 2500 and 4500 runs and sounds nice no missing no smoke.
Answer It is difficult to interpret a noise from a distance. However, a mechanics stethescope is good for this sort of thing. Or use a length of wood to listen to the noise. If it is a bearing then you will be able to follow the sound of the vibration with the length of wood or the stethescope. It might also be an air leak at the manifold gasket--spraying oil at the suspected area could confirm that. (An alternator bearing can exhibit this type of behavior.)
