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Has anyone tried using a graphite piston in a low performance IC engine?
I have a 3/8 inch bore 1/2 stroke horizontal hit-miss engine using cast iron cylinder and piston. Using an oil cup at the bottom end of the cylinder for piston lubrication. It takes about 2 drops of oil every half hour to keep it happy. No problem there.
I am THINKING about a vertical version. The oil cup lubrication will not work out very well there. I have tried using a fuel/oil mix on the horizontal with all sorts of oil types and fuel types and all tend to carbon up the engine after about 10 hours or so. Not much of a problem with larger engines, but with such small valves it only takes a little bit of carbon to keep a valve from seating. The oil cup lube eliminated this problem so I really don't want to go back to fuel/oil mixes if I can avoid it.
So the question is will an graphite piston without lubrication work for this. Graphite has a lower coefficient of expansion than cast iron so it may loosen up a bit as the engine comes up to operating temperature, but on the horizontal the cylinder temperature never gets above 120 deg F so I don't think that will be a problem in this size. Besides the piston will run hotter than the cylinder so that will also minimize it. I have plenty of room to increase the piston crown and wall thickness to make up for the lower strength of the graphite.
Any one have any thoughts or experience on this?
Gail in NM
I have a 3/8 inch bore 1/2 stroke horizontal hit-miss engine using cast iron cylinder and piston. Using an oil cup at the bottom end of the cylinder for piston lubrication. It takes about 2 drops of oil every half hour to keep it happy. No problem there.
I am THINKING about a vertical version. The oil cup lubrication will not work out very well there. I have tried using a fuel/oil mix on the horizontal with all sorts of oil types and fuel types and all tend to carbon up the engine after about 10 hours or so. Not much of a problem with larger engines, but with such small valves it only takes a little bit of carbon to keep a valve from seating. The oil cup lube eliminated this problem so I really don't want to go back to fuel/oil mixes if I can avoid it.
So the question is will an graphite piston without lubrication work for this. Graphite has a lower coefficient of expansion than cast iron so it may loosen up a bit as the engine comes up to operating temperature, but on the horizontal the cylinder temperature never gets above 120 deg F so I don't think that will be a problem in this size. Besides the piston will run hotter than the cylinder so that will also minimize it. I have plenty of room to increase the piston crown and wall thickness to make up for the lower strength of the graphite.
Any one have any thoughts or experience on this?
Gail in NM