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After 6 or 7 pounds the ice gets thin on stock pistons in stock bores. Not that detonation and preignition aren’t issues the real point is power is developed by heat. Heat makes tge pressure that pushes the piston that turns the crank converting the heat of combustion into rotational force at the crankshaft.
Detonation/preignition is what you’re trying to suppress with the E85. Heat is another issue measured in BTU’s it is a function of how much mixture is passing through the engine. To that end the problem gets to be the piston gets hot and looses physical strength on one hand and expands on the other. Included in the expansion of things that get hot are the rings. Starting here stock end clearance rings not meant for dealing with transferring more heat than designed for meeting emission requirements will expand taking up the end clearance. Once gone they will bind ones pooch upward and outward the result being gouged cylinder walls and broken ring lands of the piston. Lower down on the piston is the skirt clearance with the cylinder wall, here the skirt will attempt to lock itself with the cylinder bore wall. In mild cases this will scratch and gouge the bore wall on the thrust sides. In severe cases the skirt and sometimes the bore wall are ripped apart.
The failure mode above is separate and apart from the distraction that detonation and preignition can do. But either mode of “overheating“ the piston or blasting it with explosive forces the factory piston quickly gives up. That is true of older low alloy castings and of the newer hypereutectic castings. Generally with the older pistons which run a looser bore clearance you get damaged walls and ring lands as these expand more than hypereutectic pistons. The hypereutectics run tighter clearances but are more thermally stable but splinter apart when they let go leaving the piston pin to hammer holes in the cylinder wall.
Detonation/preignition usually overheats the upper ring land and the ring. The aluminum on the quench side overheats melting away to the ring grooves failing the rings as it goes till finally burning through to the crankcase side at of under the oil ring groove. I keep one example on my desk as a pen/pencil holder. Here a forged piston is much more immune than any casting but not necessarily one hundred percent successful at it.
So without replacing pistons with forging and dressing up internal clearances and bearings 390 to 400 hp with a supercharge or nitrous is about the physical limit of sustained operation. You can go higher in bursts for a few seconds but keep in mind that pistons fail even on dyno pulls which last but a few seconds, so when trouble comes on it does so mighty fast. This is somewhat the same for naturally aspirated on these parts where about 400 hp can be had in bursts but not continuously operated there. The reason being how much heat is generated in the cylinder against how fast it can be removed either as work into the crankshaft and by the cooling system against how the material’s strength profiles change with temperature.
If I were in your shoes I’d expect an old engine will eat its insides in no time at all and that the destruction will be pretty complete rendering not much if anything salvageable.
Bogie
Detonation/preignition is what you’re trying to suppress with the E85. Heat is another issue measured in BTU’s it is a function of how much mixture is passing through the engine. To that end the problem gets to be the piston gets hot and looses physical strength on one hand and expands on the other. Included in the expansion of things that get hot are the rings. Starting here stock end clearance rings not meant for dealing with transferring more heat than designed for meeting emission requirements will expand taking up the end clearance. Once gone they will bind ones pooch upward and outward the result being gouged cylinder walls and broken ring lands of the piston. Lower down on the piston is the skirt clearance with the cylinder wall, here the skirt will attempt to lock itself with the cylinder bore wall. In mild cases this will scratch and gouge the bore wall on the thrust sides. In severe cases the skirt and sometimes the bore wall are ripped apart.
The failure mode above is separate and apart from the distraction that detonation and preignition can do. But either mode of “overheating“ the piston or blasting it with explosive forces the factory piston quickly gives up. That is true of older low alloy castings and of the newer hypereutectic castings. Generally with the older pistons which run a looser bore clearance you get damaged walls and ring lands as these expand more than hypereutectic pistons. The hypereutectics run tighter clearances but are more thermally stable but splinter apart when they let go leaving the piston pin to hammer holes in the cylinder wall.
Detonation/preignition usually overheats the upper ring land and the ring. The aluminum on the quench side overheats melting away to the ring grooves failing the rings as it goes till finally burning through to the crankcase side at of under the oil ring groove. I keep one example on my desk as a pen/pencil holder. Here a forged piston is much more immune than any casting but not necessarily one hundred percent successful at it.
So without replacing pistons with forging and dressing up internal clearances and bearings 390 to 400 hp with a supercharge or nitrous is about the physical limit of sustained operation. You can go higher in bursts for a few seconds but keep in mind that pistons fail even on dyno pulls which last but a few seconds, so when trouble comes on it does so mighty fast. This is somewhat the same for naturally aspirated on these parts where about 400 hp can be had in bursts but not continuously operated there. The reason being how much heat is generated in the cylinder against how fast it can be removed either as work into the crankshaft and by the cooling system against how the material’s strength profiles change with temperature.
If I were in your shoes I’d expect an old engine will eat its insides in no time at all and that the destruction will be pretty complete rendering not much if anything salvageable.
Bogie
