I agree with the possibility of rings. When an engine runs rich for a while, they wash the oil film off the cylinder walls and the rings round edges and polish the bores. One that happens, it's a runaway feedback loop and just progressively gets worse. This also lowers the octane of the fuel by adding oil vapor to the mixture, causing MORE un-burned fuel, causing MORE cylinder wall damage etc etc etc.
Can you post some close ups of the cylinder walls?
We have a DBilas ITB m20 car here at the shop right now. The previous shop had botched all kinds of things and caused cylinder wash down. We pulled the oil pan and pistons in situ, deglazed the cylinder walls, found 4 cylinders with rings not only stuck in the lands, but three top rings and one second ring was actually broken. New rings, plop it back together and this time will get a proper tuning session. I've had several of these type jobs over the years - and the very reason I keep repeating that the m20 does not need to go with larger injectors, specially a stock one.
Can you post some close ups of the cylinder walls?
We have a DBilas ITB m20 car here at the shop right now. The previous shop had botched all kinds of things and caused cylinder wash down. We pulled the oil pan and pistons in situ, deglazed the cylinder walls, found 4 cylinders with rings not only stuck in the lands, but three top rings and one second ring was actually broken. New rings, plop it back together and this time will get a proper tuning session. I've had several of these type jobs over the years - and the very reason I keep repeating that the m20 does not need to go with larger injectors, specially a stock one.
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