These Darton Subaru "DRY" WRX EJ20 sleeves are designed to replace your factory cylinder liners with a stronger, more durable, and longer lasting ductile iron surface that can hold more power, and be bored further than stock. Many engine blocks cannot take excessive boring, or high boost circumstances without failing. Switching to a Darton Dry sleeve will solve this problem.
Subaru blocks are made out of aluminum and can sometimes react adversely to heat, slightly changing clearances with temperature changes, consequently making the engine less consistent and less reliable. Inserting a Ductile Iron Dry Sleeve into an aluminum Subaru block reduces the amount of warp, and remains a consistent size and shape through its operating heat range.
DRY SLEEVE, means that the sleeve does not contain water/coolant passages bored through the Subaru WRX EJ20 sleeves. This solid design provides a more rigid structure to prevent warping and sleeve expansion.
Darton manufactures ductile iron sleeves for dry installation in aluminum blocks with special surface finishes and recommends that aluminum block cylinder walls be lightly honed with "Brush Research" bumble hones prior to sleeve installation. The combination of male and female surface preparation greatly enhances heat transfer when the sleeves are installed and fit properly.
NOTE: ALL Darton Sleeves come from the factory slightly smaller than stock bore. ALL Darton sleeves must be finish bored and honed to the specs of the pistons going into them. You CAN NOT install a piston into ANY Darton sleeve the way it arrives from the factory. This ensures that you will get the exact proper piston-wall clearance to provide a tight seal in your engine. Your machine shop already knows this, and now so do you.