scratches on piston head and tapping noise

[rogus]

I recently bought a rebuilt sbc 355 after being able to hear it run. After installing it I get a loud tapping noise from the number 8 cylinder. I used a camera to see inside the piston chamber thinking something might have gotten into it through the intake manifold but there was nothing there. There was however a number of scratches on the top of the piston head between the valve reliefs (4 opposing valve reliefs separated by the middle top of the piston). It's the middle between the valve reliefs that is scratched up. I ran the camera into the number 4 piston chamber to see if it had scratches on the piston head there as well but it didn't. Not sure what is causing this? Any help would be appreciated.

 

[CopperNick]

So my question to you at this point is, Do you suspect the presence of matching scratches or other damage on the faces of the valves in the cylinder? If so, a normal camera can't swivel to look up and see the valves but a bore camera can. Basically it is the same kind of inspection tool as what the plumbers use to scope sewer and water lines to look for damage or blockage, only a lot smaller to get into tighter places.

Also, have you gone ahead and removed the valve cover and physically attempted to move the rocker or the pushrod to see if they are loose?

After that, have you given any consideration to removing the oil filter and filleting it to retrieve the filter media from inside the canister so you can spread it and check it for debris or micro-shrapnel?

Finally, is your peace of mind worth the $$ for the gaskets and the labor necessary to remove the intake and see what's to be seen down in the valley, and then, finding nothing in there, go the next step and pull the head completely???

You say you are seeing scratches and that, to me, is a symptom. Up to you as to how deep the dive will be before you get an answer to what caused those scratches and what will have to be done to fix the issue.



Nick

 

[rogus]

So my question to you at this point is, Do you suspect the presence of matching scratches or other damage on the faces of the valves in the cylinder? If so, a normal camera can't swivel to look up and see the valves but a bore camera can. Basically it is the same kind of inspection tool as what the plumbers use to scope sewer and water lines to look for damage or blockage, only a lot smaller to get into tighter places.

Also, have you gone ahead and removed the valve cover and physically attempted to move the rocker or the pushrod to see if they are loose?

After that, have you given any consideration to removing the oil filter and filleting it to retrieve the filter media from inside the canister so you can spread it and check it for debris or micro-shrapnel?

Finally, is your peace of mind worth the $$ for the gaskets and the labor necessary to remove the intake and see what's to be seen down in the valley, and then, finding nothing in there, go the next step and pull the head completely???

You say you are seeing scratches and that, to me, is a symptom. Up to you as to how deep the dive will be before you get an answer to what caused those scratches and what will have to be done to fix the issue.



Nick

Also, have you gone ahead and removed the valve cover and physically attempted to move the rocker or the pushrod to see if they are loose?

I have the valve cover pulled. Planning on checking the rockers/pushrods next.

After that, have you given any consideration to removing the oil filter and filleting it to retrieve the filter media from inside the canister so you can spread it and check it for debris or micro-shrapnel?

Got to admit I hadn't thought of that.

Finally, is your peace of mind worth the $$ for the gaskets and the labor necessary to remove the intake and see what's to be seen down in the valley, and then, finding nothing in there, go the next step and pull the head completely???

With as loud as that tapping noise is I don't think I have a choice. I must admit however that this is new territory for me in that I am not sure what I'm looking for...unless I find a nut or washer or anything else that might be blaringly obvious it doesn't belong there. If I pull the head and see marks on the valves I'll need to be back here looking for diagnostic help and just hope it doesn't come to that.