Index

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The piston, which is oil-cooled and of the monobloc type made of nodular cast iron, is equipped with 3 compression rings and 1 scraper ring.

By use of a combination of compression rings with different barrel-shaped profiles and chrome-plated running surface on all rings, the piston ring pack is optimized for maximum sealing effect and minimum wear rate.

The piston has a cooling oil space close to the piston crown and the piston ring zone. The heat transport, and thus the cooling effect are based on the shaker effect arising during the piston movement. Oil from the engine's lubricating oil system is used as cooling oil.

The piston is provided with a turned edge at the top due to the flame ring mounted in the cylinder liner.

Piston Pin

The piston pin is fully floating which means that it can turn freely in the pin bosses of the piston as well as in the connecting rod bush. The piston pin is turned in place upwords in axial direction by two circlips (seeger rings).

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The connecting rod is die-forged. The big-end has an inclined joint in order to facilitate the piston and connecting rod assembly to be withdrawn up through the cylinder liner. The joint faces on the connecting rod and the bearing cap are serrated to ensure precise location and to prevent relative movement of the parts.

The big-end bearing is of the trimetal type, i.e. steel shells lined with tin-aluminium or lead-bronze coated with a running layer. Designed as plain type or rillentype. The bearing shells are of the precision type and are therefore to be fitted without scraping or any other kind of adaption.

The small-end bearing is of the trimetal type and is pressed into the connecting rod.

Cylinder Liner

The cylinder liner is made of fine-grained, pearlite cast iron and is fitted in a bore in the engine frame. Replaceable cast iron sealing rings are fitted between the liner and the cylinder head and between the liner and the frame. The liner is clamped by the cylinder head and is guided by a bore at the bottom of the cooling water space of the engine frame. The liner can thus expand freely downwards, when heated during the running of the engine. Sealing for the cooling water is obtained by means of silicone rubber rings which are fitted in grooves machined in the liner.

The cylinder liner is of the socalled "stepped cylinder" type, provided with flame ring inserted in the top of the liner.

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L23/30H

Preparations before Dismounting

1) Clean the upper part of the cylinder. If not, the piston may get stuck during removal in the carbon deposited in this area.

a)Turn the piston to the buttom.

b)Place a used piston ring on top of the piston.

c)Mount the tube (for holding down the cylinder liner during the piston withdrawal) on one of the cylinder head studs, screw on the nut and tighten it slightly.

d)Turn the piston in top, in order to push the flame ring out of the cylinder by means of the piston ring.

Info: It is the used piston ring which pushes the flame ring out of the cylinder.

2)Remove the gangway, if any installed, in order to improve the access conditions.

3)Turn the crankshaft to bring the crank throw concerned into a position of approx. 50 degrees before TDC.

This position is identifiable by the connecting rod shaft being very close to the cylinder liner shirt, see fig. 1.

4)Clean the threaded hole in the piston top, and mount the eye screw.

5)Mount the tube (for holding down the cylinder liner during the piston withdrawal) on one of the cylinder head studs, screw on the nut and tighten it slightly.

6)Attach a wire rope to the eye bolt by means of a shackle, hook the wire on to a tackle and pull the wire rope tight.

Note! If minor adjustments of the crank throw position appear necessary for access to the connecting rod screws, the wire rope must be slackened before turning of the crankshaft and tightened up again in the new crank throw position.

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Note! The purpose of the guide pin is to prevent any damage of crank journal, joint faces or bearing surface to occur during dismounting of the bearing cap, and to facilitate easy handling when removing the bearing cap from the crankcase.

9)Remove the screwdriver from the guide pin, and dismount the bearing cap by sliding it along the guide pin, see fig 2.

10)Remove the guide pin from the connecting rod.

Dismounting of Upper Big-end Bearing Shell

11)Pull the piston and connecting rod assembly upwards and remove the upper big-end bearing shell, see fig 3.

12) Lift the piston and connecting rod assembly up through the cylinder liner and out of the engine, see fig 4.