The piston is the moveable floor of the combustion chamber that rises and falls in the cylinder according to the stages of the 4-cycle internal combustion engine. On the intake stroke the piston descends, creating low pressure in the cylinder while the intake valve is open, and atmospheric pressure forces in the air/fuel mixture. On the compression stroke the intake valve closes and the piston rises, compressing the air/fuel mixture and increasing the temperature of the charge. When the piston is near the top of its travel (known as Top Dead Center, or TDC) the spark plug ignites the mixture and the combustion pressure forces the piston downward. Finally, on the exhaust stroke, the piston rises as the exhaust valve is open, forcing the spent gases out of the cylinder.

The piston is attached to the small end of the connecting rod with a hardened steel pin, typically called a wrist pin. The pin can be a press fit in the connecting rod bore and free to turn in the piston bore, or it can be “fully floating” and free to turn in each component. Such pins must be retained in the piston with circlips to prevent sideways movement and contact with the cylinder wall. The piston skirt is the area between the bottom ring groove and the bottom of the piston. This is the bearing surface of the piston where it contacts the cylinder wall. Wear in this area, called “scuffing”, can be caused by lack of lubrication or lack of clearance due to bore distortion. To help prevent scuffing, many pistons today come with moly coated skirts. This coating reduces friction and allows very tight piston-to-cylinder wall clearance.

Like the pedals on a bicycle, the pistons are the mechanical components that bear the force that is ultimately turned into vehicle motion. While leg muscles generate the pressure on the bicycle pedals, it is the pressure from combustion in the cylinders that propels the pistons. The pistons in turn drive the connecting rods, which turn the crankshaft, transmission gears and driveline components that end up turning the wheels.

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    • (0 reviews)
      # sp21551
      Sportsman Connecting Rods by Crower®. Forged from the best aircraft quality steel. Sportsman’s come standard with aircraft quality 3/8 8740 steel alloy cap screw bolts rated at 180,000 p.s.i.
      Designed to deliver trouble-free, consistent performanceRight for your vehicle and lifestyle
      $491.99 - $751.65
    • (0 reviews)
      # sp21541
      Maxi-Light Steel Billet Connecting Rods by Crower®. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this experience with...
      Designed to deliver trouble-free, consistent performanceRight for your vehicle and lifestyle
      $1,870.04
    • (0 reviews)
      # sp21534
      Connecting Rod Bushings by Crower®. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this experience with our manufacturing...
      Designed to deliver trouble-free, consistent performanceRight for your vehicle and lifestyle
      $103.28
    • (0 reviews)
      # sp21533
      Universal Connecting Rod Bolt by Crower®. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this experience with our manufacturing know...
      High quality at an affordable priceExpertly made from premium materials
      $60.43 - $261.24
    • (0 reviews)
      # mpn358501119
      Sportsman Connecting Rods by Crower®. Set of 8. Connecting Rod made from Forged 4340 Steel. Forged from the best aircraft quality steel. Sportsman’s come standard with aircraft quality 3/8 8740 steel alloy cap screw bolts rated...
      High quality at an affordable priceExpertly made from premium materials
      $751.65
    • (0 reviews)
      # mpn358501117
      Maxi-Light Steel Billet Connecting Rods by Crower®. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this experience with our...
      High quality at an affordable priceExpertly made from premium materials
      $1,870.04
    • (0 reviews)
      # mpn358501121
      Sportsman Connecting Rods (SP93231B-4) by Crower®. Set of 4. Ford in a cap screw design. Forged from the best aircraft quality steel. Ford Sportsman’s come standard with aircraft quality 3/8 8740 steel alloy cap screw bolts rated...
      High quality at an affordable priceExpertly made from premium materials
      $491.99
    • (0 reviews)
      # mpn358501122
      Sportsman Connecting Rods (SP93234B-4) by Crower®. Set of 4. Connecting Rod made from Forged 4340 Steel. Ford in a cap screw design. Forged from the best aircraft quality steel. Ford Sportsman’s come standard with aircraft...
      High quality at an affordable priceExpertly made from premium materials
      $491.99
    • (0 reviews)
      # mpn358501107
      12-Point 7/16" X 2.320" Connecting Rod Bolt (90804-1) by Crower®. 1 Piece. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this...
      High quality at an affordable priceExpertly made from premium materials
      $28.37
    • (0 reviews)
      # mpn358501110
      12-Point 3/8" X 1.600" Connecting Rod Bolt (90828-1) by Crower®. 1 Piece. For SB Sportsman Rod. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower...
      High quality at an affordable priceExpertly made from premium materials
      $12.82
    • (0 reviews)
      # mpn358501115
      Connecting Rod Bushings (90927N-8) by Crower®. 0.927" Pin 1.100" OAL .982" dia. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower...
      High quality at an affordable priceExpertly made from premium materials
      $103.28
    • (0 reviews)
      # mpn358501114
      Connecting Rod Bushings (90927-8) by Crower®. 0.927" Pin 1.055" OAL .997" dia. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower...
      High quality at an affordable priceExpertly made from premium materials
      $103.28
    • (0 reviews)
      # mpn594432
      CHQ™ Piston Set (EP-631) by Auto Metal Direct®, 8 Pieces. 0.3 Over. Hi-Tech Hypereutectic High Performance Pistons are fully designed, tested, and certified by a QS-9000 and ISO-9001 OE manufacturer with 30 years experience in...
      Direct fit replacementMade according to OE specs
      $411.24
    • (0 reviews)
      # mpn594433
      CHQ™ Piston Set (EP-632) by Auto Metal Direct®, 8 Pieces. 0.4 Over. Hi-Tech Hypereutectic High Performance Pistons are fully designed, tested, and certified by a QS-9000 and ISO-9001 OE manufacturer with 30 years experience in...
      Direct fit replacementMade according to OE specs
      $411.24
    • (0 reviews)
      # mpn594434
      CHQ™ Piston Set (EP-633) by Auto Metal Direct®, 8 Pieces. 0.6 Over. Hi-Tech Hypereutectic High Performance Pistons are fully designed, tested, and certified by a QS-9000 and ISO-9001 OE manufacturer with 30 years experience in...
      Direct fit replacementMade according to OE specs
      $411.24
    • (0 reviews)
      # mpn594431
      CHQ™ Piston Set (EP-630) by Auto Metal Direct®, 8 Pieces. Hi-Tech Hypereutectic High Performance Pistons are fully designed, tested, and certified by a QS-9000 and ISO-9001 OE manufacturer with 30 years experience in piston...
      Direct fit replacementMade according to OE specs
      $411.24
    • (0 reviews)
      # mpn358501108
      Universal 12-Point 7/16" x 1.800" Connecting Rod Bolt Kit (90820-16) by Crower®. Set of 16. Connecting Rod Bolt made from H-11 tool Steel. Designed to fit Crower steel billet and titanium connecting rods. Torque to 75 ft.-lbs. 220...
      High quality at an affordable priceExpertly made from premium materials
      $261.24
    • (0 reviews)
      # mpn358501111
      Universal 12-Point 7/16" X 1.540" Connecting Rod Bolt (90830-1) by Crower®. 1 Piece. AMS-5844. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower...
      High quality at an affordable priceExpertly made from premium materials
      $60.43
    • (0 reviews)
      # sp21552
      Steel Billet Connecting Rods by Crower®. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this experience with our...
      Designed to deliver trouble-free, consistent performanceRight for your vehicle and lifestyle
      $2,996.38
    • (0 reviews)
      # mpn358501120
      Sportsman Connecting Rods (SP93206B-8) by Crower®. Set of 8. 6.00" Length, 2.100" Pin. Connecting Rod made from Forged 4340 Steel. Ford in a cap screw design. Forged from the best aircraft quality steel. Ford Sportsman’s come...
      High quality at an affordable priceExpertly made from premium materials
      $704.45
    • (0 reviews)
      # mpn358501116
      Steel Billet Connecting Rods by Crower®. Set of 8. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower combines this experience with our...
      $2,996.38
    • (0 reviews)
      # mpn358501118
      Sportsman Connecting Rods by Crower®. Set of 8. First introduced back in 1987, the Crower Sportsman rod was the original high performance stock replacement rod. Features traditional thru-bolt and nut fasteners for stock legal...
      High quality at an affordable priceExpertly made from premium materials
      $731.59
    • (0 reviews)
      # mpn358501109
      Universal 12-Point 7/16" x 1.540" Connecting Rod Bolt Kit (90826A-16) by Crower®. Set of 16. Perfect combination of power and mileage with extended rpm range. Works well with stock and near-stock engines and drive trains. Crower...
      High quality at an affordable priceExpertly made from premium materials
      $141.74


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    Pistons are cast or forged from aluminum alloy. Hypereutectic pistons are a type of cast piston that is used in high performance engines. They have a higher concentration of silicone in the alloy, which increases their hardness, wear resistance, and durability. The forging process increases strength and resistance to damage, and forged pistons are generally used for extreme conditions like racing. Although pistons are a tight fit in the cylinders, with clearances for some engines at 0.001” or even less, for effective combustion chamber sealing piston rings are used. These fit into grooves near the top of the piston, called the crown, or head, and ride against the cylinder walls. The most common configuration is 2 compression rings with a 3rd ring below them for oil control.

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