Oldsmobile 12518282 Ring Unit, Piston(Std)

There are times that when a pistons is needed to be fixed properly to its same reciprocating connecting rod its more advisable to leave it to a professional and has to use an arbor press. New piston rings should be in the size of the piston in use and it is important for a rebuilt engine to have them fitted. To do this, place the piston rings through each set carrying the rap ring a 2nd ring and a three-piece oil control ring and measure the ring end gap for all of them. Place the first top ring into the cylinder bore in the manner with the ring shoulder placed about 1/4 inch below the top of the ring travel and the ring perpendicular to the cylinder wall. In the case where there is lack of space to insert the feeler gauge under the ring's ends-replace the ring. Roll each piston ring around the piston to feel if there is any binding of the ring in its groove; replace any distorted ring. When fitting the rings, the gaps have to be in the correct places, if possible use a piston ring expander on the rings or small lengths of tinning. The lower and upper steel oil ring rails together with gap location, installation process of bottom oil ring spacer and its parts. The same should be done on the second and the top rings and the gaps should also be well arranged. Last, take a blade feeler gauge and check the piston ring clearance in its grooves, trapped in the piston rotating it to make sure that the correct clearance is provided and do the needful as per the case and replace.

The piston must be connected to the proper connecting rod and that needs to be done by a professional with the help and an arbor press. Piston rings should also be new and in the correct size to fit the piston being used and their fit is very important for the performance of the rebuilt engine. Before fitting piston rings, the ring end gap for each ring should be measured and the piston rings should be grouped into sets with a top ring, a second ring and an oil control three piece ring. Place one top ring approximately ¾-inch below the upper limit of ring travel and must be perpendicular with the cylinder bore by using the top portion of a piston. If with a feeler gauge, you cannot get the distance between the two ends of the ring sufficient, replace the present one with another top ring. Do the same for all other top rings and, if necessary, file the ends of them to shape. Also, it is important to measure the end gap of each second ring, as well as oil control rings. Refer to figures 3 and 4 and roll each piston ring on the piston to verify that none of the rings bind in their grooves; if the rings have been distorted, replace them. It is essential that the gaps are aligned correctly to the cylinder bore when installing the piston rings and this can be done with a piston ring expander if available or thin strips of tin if the expander is not available. Place the bottom oil ring spacer and its parts to specify the positions of the gaps for the steel oil ring rails. Last of all, inspect the fit of the piston rings into their grooves with the blade feeler gauge and rotate the piston around to make sure there is enough gap and replace or adjust the rings correspondingly.

Carefully file the ring ends with a fine file to increase the gap.

Proceed to install the rings on the pistons.

Excess end gap is not critical unless it exceeds 0.030 to 0.035 inches, so double-check the rings for compatibility.