I have owned since new a 2006 Honda Accord 2.4L (K24A8) 180,000 highway mi., always Mobil 1 synthetic oil every 5-7K. It started using more and more oil over the past few years, now using over 2 qt. every 350 mi.(no external leaks). Currently I have it torn down to replace a burnt exhaust valve and the piston rings (thinking the rings were causing the oil problem). We think the bunt valve is likely caused by piston carbon deposits and possibly the start of the catalytic converter plugging (due to oil burn) which created exhaust back pressure and allowed a carbon deposit to stick to valve. Will need to remove cat. converter to verify.

Problem: Looking at the parts I do not see anything obvious which would cause excessive oil consumption. What am I missing?

#1 (Top) Rings - Old #1 ring gaps are 0.65 mm and are just outside the 0.60 mm service limit. New ring gap measures 0.40 mm and is just outside 0.20-0.35 mm range but well within service limit.
#2 Rings - Old #2 ring gaps are well outside service limit of 0.70 mm & measure 1.05 mm. New ring gap measures 0.50-0.55 mm is within correct range 0.40-0.55 mm.
Old ring gaps are 0.70 mm and within service limit of 0.80 mm. New ring gap measures 0.35 mm and in correct range 0.20-0.70 mm.

Bore gauge check show all cylinder are within spec. per Honda service manual.

The Head was professionally rebuilt at 155,000 mi. (uses same amount of oil before and after rebuild). The machine shop now has the head for inspection, new valve & whatever is deemed appropriate. I've read seal leaks would cause encrusted carbon on stem and valve in port., mine looked normal. The PCV valve was also replaced.

Honda service manual states when replacing piston rings "Only a scored or scratched cylinder bore must be honed." My bores have no top ridges and feel smooth, no scoring or scratches (see picture below). There are rubbed areas where piston and rings traveled. Certainly no scratches which would catch a fingernail or run the length of the cylinder.

Old school engine guys are saying one should cross hatch (at least flex hone) the the bore when installing new rings. Does Honda do something different with their cylinder/rings to avoid this process?

Thank you for the help.

 

Show pics of the head

 

If you installed new piston rings, you should have honed the block. Not doing so will not allow the engine/piston rings to seat. Causing you to burn oil.