My 97 LX450 (250k)overheated on the coldest morning this past February. Maybe a stuck thermostat? Fan clutch? I don't know. Started later that afternoon and steam was coming out at every joint in the exhaust and I got a misfire code. I did not drive it again. A few weeks later I pulled the head off and it was clearly blown. Piston #6 was shiny while the rest were covered in carbon. There was also a good bit of antifreeze that came out of the oil pan. My plan was a complete reseal and valve job until I was checking the cylinder bores. At the top front of cylinder #1. Starting about 3/8" down from where that rings stop you could feel where the ring had dug into the cylinder so that it got uniformly deeper as it got closer to the top of the stroke. Anyway, I pulled the engine block and transmission/transfer case. I purchased oem 50 over pistons and rings and took it to the machine shop to be bored. So my choice now is to spend money I don't have and reorder 100 over pistons and rings and or (if he can find one) let him bore the cylinder and sleeve it.
I have not found anyone in my area that is familiar with our vehicles (machinist included), but he says that he has seen this problem in quite a few domestic inline sixes that have the water pump up front. Has any one else seen this or had success sleeving the block? The rest of the cylinders looked and measured great. Also all the rod and main bearings looked great and measured out to .0015 oil clearance with plastigage. The coolant passages in the block were very clean, as was the oil cooler. The PO replaced the pesky heater hose and radiator after that hose blew. I have had it for 5yrs 30k and that was done at least a year before I purchased it.
I have not found anyone in my area that is familiar with our vehicles (machinist included), but he says that he has seen this problem in quite a few domestic inline sixes that have the water pump up front. Has any one else seen this or had success sleeving the block? The rest of the cylinders looked and measured great. Also all the rod and main bearings looked great and measured out to .0015 oil clearance with plastigage. The coolant passages in the block were very clean, as was the oil cooler. The PO replaced the pesky heater hose and radiator after that hose blew. I have had it for 5yrs 30k and that was done at least a year before I purchased it.