liferider
Looking forward to retirement
Ok, Talked to a Custom engine builder who specializes in V twins and loves evo's. I am pulling my heads and shipping them to him where he is going to Deck them. Also he is shipping back with my heads to me the correct injectors. He builds these evo's set ups for people all the time he said. Stock evo engines are 45-50 HP. With the Arlen Ness EHC,Andrews 27 cam, the new injectors, the 2 into 1 thunder header, and decking and polishing the heads I should be at 70-75 HP. Decking the heads the amount he does increases compression from the stock 9-1 compression up to 10-1 compression. My local mechanic will Dyno before and after so we will get a clear picture of what it does.
built for longevity, not for peak performance, said Tom Doggett of Strokers USA, Inc. Harley de-tunes the Evolution engine by making the head ports less efficient. Doggett said he can increase the engine’s fuel efficiency and boost its horsepower by porting and decking the heads. During the interview, for this Tech Tip, Doggett, a factory-certified Harley-Davidson® Master of Technologies, talked about laminar flow, boundary layers, and experimental wings on Navy jet aircraft. There is a tremendous amount of art and science involved in making large volumes of air move where you want it to go. Proper porting increases the flow of air from the carburetor through the head and out the exhaust pipe. Air flows fastest along a straight line, it slows when it turns and slows dramatically when it hits a sharp bend. Porting removes some of the obstacles in the path of the air by smoothing the rough edges inside the intake and exhaust passages in the heads. Doggett removes the lip around the valve seat and the casting flaws. He also rounds out the corners in the air passages. After reshaping the intake and exhaust ports, Doggett uses a fine polishing compound to apply a mirror finish to the exhaust port and combustion chamber. The polished surface resists the build up of carbon deposits. Carbon is a byproduct of the burning of gasoline. It sticks to the combustion chamber in the head and to the exhaust port. This clogs the hole and restricts the outward flow of hot exhaust gases—lessening efficiency. Surprisingly, Doggett does not polish the intake port. A rough surface keeps the gasoline-rich air from sticking to the intake wall. If the port was polished, fuel droplets would puddle along the wall and would not burn efficiently in the combustion chamber. To further improve the performance potential of the stock Harley cylinder head, Doggett shaves approximately 40 thousandths of an inch (.040”) from the gasket surface with a milling machine. This process, called decking, will raise the stock 9 to 1 compression ratio to 10 to 1. The compression ratio is the amount the rising piston will squeeze the air and fuel inside the combustion chamber. “The tighter you squeeze the air mixture, the more horsepower you get out of it,” Doggett said. Of course when you increase the compression ratio, you must use a higher-octane gasoline. There are practical limits to increasing compression. Doggett said, “The best thing to do, performance wise, is to alter the heads.” After porting the heads to increase horsepower and performance on a Harley, a hotter cam and carburetor can be installed to move more fuel/air into the combustion chamber. Doggett will also port the intake manifold to match the heads. A good ignition and tuned exhaust system completes the package. Doggett recommends the 2 into 1 Thunderheader exhaust system. “It’s not pretty, but it works pretty well,” Doggett said. A pair of drag pipes actually robs horsepower from the engine. Strokers USA, Inc. can turn around a pair of heads within a week. Some facts about heads: In a naturally aspirated engine (no blower, no turbo), air is pushed into the head at 14.7 pounds per square inch (PSI) at sea level. The intake port and valve are larger than the exhaust valve and port because the exhaust only needs to flow 80 percent of the intake, due to the fact that exhaust gasses are forced out of the head at 1,600 to 1,800 PSI.
Filed under Tech Talk · Tagged with decking
built for longevity, not for peak performance, said Tom Doggett of Strokers USA, Inc. Harley de-tunes the Evolution engine by making the head ports less efficient. Doggett said he can increase the engine’s fuel efficiency and boost its horsepower by porting and decking the heads. During the interview, for this Tech Tip, Doggett, a factory-certified Harley-Davidson® Master of Technologies, talked about laminar flow, boundary layers, and experimental wings on Navy jet aircraft. There is a tremendous amount of art and science involved in making large volumes of air move where you want it to go. Proper porting increases the flow of air from the carburetor through the head and out the exhaust pipe. Air flows fastest along a straight line, it slows when it turns and slows dramatically when it hits a sharp bend. Porting removes some of the obstacles in the path of the air by smoothing the rough edges inside the intake and exhaust passages in the heads. Doggett removes the lip around the valve seat and the casting flaws. He also rounds out the corners in the air passages. After reshaping the intake and exhaust ports, Doggett uses a fine polishing compound to apply a mirror finish to the exhaust port and combustion chamber. The polished surface resists the build up of carbon deposits. Carbon is a byproduct of the burning of gasoline. It sticks to the combustion chamber in the head and to the exhaust port. This clogs the hole and restricts the outward flow of hot exhaust gases—lessening efficiency. Surprisingly, Doggett does not polish the intake port. A rough surface keeps the gasoline-rich air from sticking to the intake wall. If the port was polished, fuel droplets would puddle along the wall and would not burn efficiently in the combustion chamber. To further improve the performance potential of the stock Harley cylinder head, Doggett shaves approximately 40 thousandths of an inch (.040”) from the gasket surface with a milling machine. This process, called decking, will raise the stock 9 to 1 compression ratio to 10 to 1. The compression ratio is the amount the rising piston will squeeze the air and fuel inside the combustion chamber. “The tighter you squeeze the air mixture, the more horsepower you get out of it,” Doggett said. Of course when you increase the compression ratio, you must use a higher-octane gasoline. There are practical limits to increasing compression. Doggett said, “The best thing to do, performance wise, is to alter the heads.” After porting the heads to increase horsepower and performance on a Harley, a hotter cam and carburetor can be installed to move more fuel/air into the combustion chamber. Doggett will also port the intake manifold to match the heads. A good ignition and tuned exhaust system completes the package. Doggett recommends the 2 into 1 Thunderheader exhaust system. “It’s not pretty, but it works pretty well,” Doggett said. A pair of drag pipes actually robs horsepower from the engine. Strokers USA, Inc. can turn around a pair of heads within a week. Some facts about heads: In a naturally aspirated engine (no blower, no turbo), air is pushed into the head at 14.7 pounds per square inch (PSI) at sea level. The intake port and valve are larger than the exhaust valve and port because the exhaust only needs to flow 80 percent of the intake, due to the fact that exhaust gasses are forced out of the head at 1,600 to 1,800 PSI.
Filed under Tech Talk · Tagged with decking
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