Mark in barrel

[jddevel]

With my block back from being rebored on close inspection I found the "mark" in the bottom part of one of the barrel walls.I did not notice on dismantling. Anyone any idea. It`s circular in shape and on enlarging the picture the outside of the "circle" is in the form of indentations rather as if made by a saw blade. I believe it wil be below the top rings. Not sure about the bottom one. The block was pressure tested and has been bored to 30 over. Before I discuss it with the engineering company I`d appreciate forum members views mark in barrel 2.jpg[/attachment]

[Steve Simmons]

This is after boring? Was it there before the boring process? It would have to have been pretty deep. I was going to say maybe some previous corrosion but perhaps it was done during machining somehow? Or possibly a casting issue? I'm not an expert though.

[jddevel]

Thanks Steve. I don`t recall it being there when the engine was dismantled but then apart from feel for wear at the top of the barrel Ididn`t really check especially as the walls showed the normal carbon deposit. I`ve added another picture plus note that the "circle" is around 10-12mm in diameter and shows no obvious continuation of the rebore marks made by the machine. I had thought initially that it was a "plug" installed at some time and the ground down but as stated the circumference of the circle I would liken to a mark made by a hacksaw blade.

[jddevel]

Sorry forgot the picture

[Rob Reilly]

I can't see any way a cutting tool of any kind could get in there to make such a mark.
Is there anything on the outside of that cylinder there that would do that, like a casting defect?
I am inclined to think it is the remains of a bad corrosion spot, perhaps where a ring gap sat idle for many years with moisture getting in.

[Duncan M]

I agree with Rob.

Not likely the machinist did it. Probably not an issue.

[Mark McCombs]

No honing marks inside the circle?

I would ask the machine shop....

[jddevel]

OK so lengthy chat with two of the engineers at the machine shop who specialize in classic and race engines. Their view is that it is a original casting issue. In their opinion with no immediate water jacket and having been pressure tested see no problem with using it as is although as the client if I wanted it sleeved they let me think it over but emphasis its location should as stated cause no problem. They have seen it before and believe it to be caused by probably a "air bubble" in the original casting and due to its location remained un-noticed may even only been exposed when the 15 thou rebore look place (was standard). They felt that as below the rings and no water jacket in the immediate vicinity I shouldn't have anything to concern myself about.