Caution
If replacement of the piston or con-rod is necessary on pistons with inserted con-rods, all components of this assembly (piston, piston rings, piston pins and con-rod) must be replaced with new components.
From engine number 19P13554 onwards, strengthened con-rods and updated con-rod bolts (M6.5) were used - take care that the new con-rod bolts are used in conjunction with the modified con-rods.
| I: | Tightening torque of M6 bolt: | 10 Nm / 7.5 lbf. ft. + 60° + 15° |
|---|---|---|
| II: | Tightening torque of M6.5 bolt: | 13 Nm / 9.5 lbf. ft. + 60° + 15° |
Assemble
Assemble guide drift from KM-634-6 (1), KM-634-7 (2) and KM-634-5 (3).
Insert new piston in woodruff key groove of KM-634-1 (1). The piston pin bore must be horizontal for this operation.
Fit KM-634-4 (3) to KM-634-1. Tighten fastening bolts to be only hind-tight.
Tension piston using KM-634-2 (2) securely to prevent it from moving.
Adjust
Determine impression depth of piston pin:
Slide assembly (1) of KM-634-6, KM-634-7 (corresponds in length to the piston pin) and KM-634-5 through piston pin bore and con-rod, until KM-634-7 is seated centrally in the piston. In this position, KM-634-4 (2) must bear against the tip of the assembly (arrows) without any play.
Tighten fastening bolts for KM-634-4.
Install
Remove KM-634-7 from guide bolt and replace with new piston pin (lubricated).
Assemble
Heat upper con-rod eye of new con-rod with heater plate. Installation temperature: 280 °C up to 320 °C. Place surface of eye flat on heater plate and reduce thermal conduction using fire-resistant brick (Illus. II).
Caution
Re-machining of the con-rod is not possible because it is not equipped with balancing studs.
Installation position: bead (1) on the con-rod is located opposite arrow on bottom of piston. Arrow on bottom of piston points to engine timing side and bead on con-rod is located on transmission side.
Firmly seated piston pin cannot be pressed further. Perform assembly quickly.
Assemble
Push assembly of KM-634-6, piston pin and KM-634-5 uniformly and without delay through piston pin bore and con-rod until it bears against KM-634-4 free of play (see illustration).
Install
Unbolt KM-634-5 and KM-634-6 (left and right) from piston pins and install piston with con-rod.