Fitting in a worn cylinder

Piston rings for a worn cylinder should be matched in the same way as for a new or rebored cylinder, but they must be tried at the lower limit of piston travel because the bore is narrowest at this point.

In connection with piston ring replacement, the cylinder bore should be honed before the rings are fitted.

Fig 1: Identifying Fitting In Worn Cylinder

Courtesy of SAAB-SCANIA OF AMERICA, INC.

1. Use a piston ring clamp to fit the rings on the piston.
2. The lower compression ring should be fitted with the side marked "top" facing up.
   Fig 2: Using Piston Ring Clamp To Fit Rings On Piston

   Courtesy of SAAB-SCANIA OF AMERICA, INC.
3. Check the fit of the piston rings in their grooves by rolling them round the grooves. Also measure the clearance at several points.
4. Oil the piston and rings before assembly. Turn the compression rings so that their gaps are roughly 180 to each other and position each of them above one of the gudgeon pin holes.
5. Make sure that the gaps in the top and bottom rings of the three-part scraper ring are staggered round the piston and not in line with each other.