I've been fighting excessive oil consumption since acquiring my car almost 2 years ago. After changing the valve guide seals and replacing the head gasket with a genuine NISMO unit, I have eliminated all external oil leaks and the engine pulls 20" of vacuum and has 190 psi compression. The only hint of oil loss is a wet spark plug on #3 and an occasional puff of blue smoke after idling at a stop light. The #3 exhaust valve is a bear to unload because of its proximity to the cam tower, so I thought I might have bunged something up. I was prepared to replace the valve guide seals again until I did a good visual inspection after pulling the valve cover.

The first thing I noticed was it was the exhaust valve next to the tower, not the inlet valve. This makes me shy away from a damaged or improperly installed inlet valve guide. Next I noticed a large puddle of oil partially covering the pipe plug between the valves. I'm now wondering what is on the other side of that plug?

If it's connected to a coolant channel, could there be a crack allowing oil seepage into the inlet port. The head was reworked in 2002. From what I can tell, it may have followed an instance of overheating for the original owner.

The car is sitting in the garage with the valve cover off, looking for some guidance here before I back it out for an inspection.

Part of the casting process. I always thought it was coolant on the other side.

Some additional notes:

After a thorough cleaning and inspection with a borescope camera, there is no visual indication of a crack anywhere in the area. However, compared to the other plugs in the head, this plug appears to sit at least one turn deeper than any of the others.

A thought: would it be worth trying to seal the thread with an RTV type of sealant to eliminate this as a leak source? If so what sealant should I use?

Blue, I understand it is part of the casting process. A sand plug is inserted into the mold to form the coolant channels. Legs attached to the sand plug pass through the opening to hold it in position during the pour. After casting, the plug is broken apart by a vibrator and passes out of the openings.

Edited May 18, 201410 yr by djwarner