pits in head cover ?

[darren mac]

Rebuilding a 175 evinrude 1992 model and I found what I call pits in the cylinder head cover and I am wondering if this is a common manufacturing defect or something that might be happening during combustion. I was a machinist for many years and I often saw these same tiny hollow spots in cast iron and aluminum when machined. These are very tiny and you have to look hard to see them. I was concerned that they somehow may cause pre- ignition. I also found these pits in other parts of the powerhead, where it had been machined. Air or other impurities will cause pits in the metal when they are cast and they show up after the metal is cut, however I am unsure if this is a manufacture issue or damage caused when the engine blew. PS I found them in the head cavities of all 6 cylinders, even those that had no problems. They are so small that I would believe that it would be hard to stick a sewing needle point in them and their depth can only be a few thousands of an inch. Has anyone seen this before or am I being too picky ? Thanks

 

[72evinrude]

Re: pits in head cover ?

Rebuilding a 175 evinrude 1992 model and I found what I call pits in the cylinder head cover and I am wondering if this is a common manufacturing defect or something that might be happening during combustion. I was a machinist for many years and I often saw these same tiny hollow spots in cast iron and aluminum when machined. These are very tiny and you have to look hard to see them. I was concerned that they somehow may cause pre- ignition. I also found these pits in other parts of the powerhead, where it had been machined. Air or other impurities will cause pits in the metal when they are cast and they show up after the metal is cut, however I am unsure if this is a manufacture issue or damage caused when the engine blew. PS I found them in the head cavities of all 6 cylinders, even those that had no problems. They are so small that I would believe that it would be hard to stick a sewing needle point in them and their depth can only be a few thousands of an inch. Has anyone seen this before or am I being too picky ? Thanks

Darren, I took my heads off today to replace spark plug threads. One and three cylinders looked like someone went crazzy with a center punch on the heads, like the alluminum exploded, so I am searching for maybe the same answer as you.

Joe (72evinrude)