My friend bought a 1987 300dt with low compression. He removed the cylinder head and sent it off to get resurfaced. He then purchased a victor reinz head gasket rebuilt kit with oil valve seals. He got the cylinder head back and reassembled it with all new gaskets. He tested the compression and all cylinder cylinders tested out to be 400. He then ran the engine for a bit. However he noticed that the victor reinz oil valve seals did not seal well and started to leak oil. He removed them and replaced them with original mercedes ones. As he was reassembling the head for the second time he noticed a hairline stratch on the fifth cylinder. Attached pictures show the stratch. The question is what could have caused this? Also, is this a major issue that he should be worried about and resurface the cylinder or just forget about it and reassemble.

Attached Thumbnails