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COBB Tuning Forged Pistons SUBARU

Brand: COBB Tuning | Category: Pistons

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More Information Year Model SubModel Cylinders Liter Aspiration Eng Desg. Fuel Notes
Click For More Info 2004 - 2007 FORESTER XT
H4 2.5 T EJ255 GAS
Click For More Info 2002 - 2007 IMPREZA WRX
H4 2.0
T EJ205
Click For More Info 2004 - 2007 IMPREZA WRX STI
H4 2.5 T EJ257 GAS
Click For More Info 2005 - 2007 LEGACY GT H4 2.5 T EJ255 ALL
Click For More Info 2005 - 2007 OUTBACK XT H4 2.5 T EJ255 ALL

Product Description

Engineered fully in-house, our pistons start life as JE low-silicone aerospace aluminum alloy forgings. From there, we CNC machine the raw forgings to our own unique design. While some features are more obvious to the eye than others.

Pistons sold as set, includes heavy duty Chromoly piston pins and clips. Additional work required includes, but is not limited to, balancing with rotating assembly and boring the cylinder walls to achieve desired clearances. We DO NOT supply pistons to be used as “drop ins”.


  • Unique 3D dish design using optimal quench area and valve relief
  • Repositioned ring package with stronger ring lands for high boost/temperature use
  • Low friction piston skirt design featuring an CNC Diamond oil retention surface finish
  • Radial Anti-detonation grooves to temper pressure spikes and enhance piston ring life
  • Accumulator groove to enhance top ring performance
  • Improved offset pin design to reduce piston slap
  • High-Strength piston pin support
  • 7mm minimum crown thickness for extra strength while still maintaining light weight
  • Precision fit wrist pin hole with pressure fed pin oiling
  • Designed to use high-quality Subaru(STi) rings

In an effort to provide better accessibility to our Forged Pistons, we have made some of the ‘standard’ piston features used on our Signature Series Short Blocks optional when purchasing the piston individually. When ordering your own custom pistons, you can decide on the options best suited to your own individual needs and budget. The follow options are what we currently make available:

Titanium Piston Pins – DLC coated to prevent galling. Extremely lightweight, high strength design we use in money-no-object, super-engine applications

Subaru(STI) Ring Set – High Quality ring set featuring chrome plated top ring, ductile iron second ring and low-friction oil scraper design.

Piston Coatings – Ceramic-based crown coating reduce heat loss and thermal shock improving power and reliability. Side skirts receive a dry moly film to reduce friction and piston noises and greatly increases cylinder life. Allows us to run tighter piston to wall clearance. Highly recommended, even factory Subaru pistons come coated!

Custom Pistons available at no extra charge – Please Call to Order

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