Figure 8-9. Checking Connecting Rod Assembly for Alignment

TM 10-3930-644-14&P

After rings have been properly fitted, install them on

piston, using a piston ring remover and installer. Take

care not to spread rings more than necessary. Stagger

ring gaps evenly around piston so that no two are in line.

Grip the connecting rod in a vise with lead lined jaws to

hold the piston firmly and roll each of the straight side

rings in its groove to be sure there are no burrs or other

interference with the free action of the ring in the groove.

The 3-piece oil ring (Figure 8-10) should be installed first

on the piston, from the top side so that the piston skirt

will not be scratched.

Figure 8-9. Checking Connecting Rod Assembly for

Alignment.

H. FITTING PISTON RINGS

Figure 8-10. Three-Piece Oil Ring

Check gap between ends of piston rings before rings are

installed on piston. Select rings to be installed on each

Install oil control ring as follows:

piston and insert them one at a time into cylinder bore in

which they are to operate. Use a piston to push ring

1. Place stainless steel expander spacer of three

squarely into cylinder bore so that it is parallel with top of

piece ring in oil groove with ends butted.

cylinder block (Figure 8-2).

2. Install steel segment on top of e pander spacer

Check the ring side clearance with a feeler gauge

with gap of segment approximately 90 beyond

(Figure 8-3) at various positions, in accordance with the

gap of stainless steel expander, making certain

tolerances

shown

TOPIC

FITS

AND

expander remains butted.

TOLERANCES.

3. Install second segment on bottom side of

expander

spacer

with

segment

gap

Measure ring to groove clearance (top of ring to top of

approximately 90 from expander spacer gap in

groove in piston). The clearances for the two engines

opposite direction from which top segment has

are specified in the following table. Use a feeler gauge

been positioned.

of the proper dimension to check the clearance.

4. Recheck installation oil control ring should be

free to move in the groove: however, a slight

Piston Ring

Clearance

drag will be noticed due to side sealing action of

F135

F163

steel segments. Make sure expander spacer

Top

.002" - .004" .002" - .0040"

remains butted.

Compression

.0015" - .0035" .0025" - .0040"

Oil Control

.000" - .005" .0025" - .0075"

R-104-1

3-31