LO 8-5 Identify and describe the configuration and construction of common cylinder block cylinder arrangements

Top-Stop Liners
Top-stop liners refer to a liner style that generally uses a heavy flange at the top of the liner Figure 43. This flange is located and centered in a precisely machined ledge recessed in the block deck. When the liner is installed in the cylinder cavity, the head gasket is positioned to sit on the edge of the flange in an area called the crimping bead Figure 44. The head gasket’s metal fire ring, combined with the flange fire dam, will seal the cylinder to prevent leakage of combustion gases into the coolant or across the block deck and down a passageway into the crankcase of the engine. When the cylinder head is tightened, the clamping force of the head is applied to the liner through the head gasket to tightly compress the liner into the counterbore Figure 45. A narrow bead of silicone is often used to help seal below the flange surface to prevent pressurized coolant from pushing around the flange to the counterbore surface. An interference fit either between the top of the flange and the block deck, or the liner area just below the flange and the block, helps seal the coolant from leaking around the liner and onto the block deck. The lower barrel of the liner typically uses a series of O-rings between the liner and the block to prevent coolant in cooling jackets (surrounding the liner) from leaking into the crankcase. Counterbores and liner O-rings are prone to leakage due to O-ring seal deterioration, liner movement, counterbore cracking, wear, and other defects of the counterbore.

FIGURE 08-43: Wet liners have a flange that sits in the cylinder block counterbore. Liner protrusion is needed to hold the liner in place and prevent it from moving.

FIGURE 08-44: Note the details of the position for the fire ring, fire dam, and liner. The metal fire ring in the head gasket helps seal compression and combustion gases in the cylinder.

FIGURE 08-45: The details of the arrangement of the head gasket, fire ring, and fire dam to seal the cylinder.

One major problem with top-stop liners is damage to the counterbore and liner flange due to the high clamping pressures of the head against the flange and the radial loads in the counterbore caused by high-temperature heating of the tightly clamped flange Figure 46. Flange cracks and breaks are also caused by excessive liner protrusion in one cylinder or uneven counterbore ledges. To reduce radial pressure in the counterbore, top-stop liners will often relocate the point where the flange is centered and is press fit to a location on the liner barrel, just below the top flange Figure 47.

FIGURE 08-46: Excessive pressure on the top-stop liner flange will cause a circumferential crack in the flange that can be very hard to detect.

FIGURE 08-47: The top-stop liner is located and centered either in the counterbore of the block deck or in an area below the counterbore to reduce counterbore damage caused by high-temperature radial loads.