Pressing out guide bushings
1 – mandrel A.60153/Ya
Check the clearance between the guide bushings and the valve stem by measuring the diameter of the valve stem and the guide bushing bore. The calculated clearance for new bushings is: 0.022–0.055 mm for intake valves and 0.029–0.062 mm for exhaust valves; maximum permissible marginal clearance (when worn out) 0.15 mm.
If the increased clearance between the guide bushing and the valve cannot be eliminated by replacing the valve, replace the valve bushings using the A.60153/R tool.
To replace the two guide bushings of the intake and exhaust valves of cylinders N1 and N4, unscrew the two studs securing the camshaft bearing housing, as they interfere with the installation of the mandrel.
Press in the guide bushings with the retaining ring fitted until the ring rests against the cylinder head plane.
After pressing, ream the holes in the guide bushings using reamers A.90310/1 (for intake valve bushings) and A.90310/2 (for exhaust valve bushings). Then grind the valve seat and bring the working chamfer width to the required dimensions as indicated above.