CHAPTER 4. REPAIR OF ENGINE

TM 5-4320-234-34

CHAPTER 4

REPAIR OF ENGINE

Section I. INTRODUCTION

overspeed governor which grounds the magneto to shut

4-1. Description

down operation if engine speed exceeds a preset limit.

The engine is a six-cylinder, four-stroke-cycle, L-

4-2. Fits, Tolerances, and Wear Limits

head, in-line, water-cooled unit which is designed to run

Table 4-1 lists the fits and tolerances applicable to

on gasoline. It is pressure lubricated by a pump located

the engine. Refer to the table to determine if you must

in the oil pan. It uses magneto ignition and an electrical

replace parts or if continued serviceability of the parts is

starter. Engine speed is controlled by a variable speed

possible.

flyball governor.

The engine is protected by an

Table 4.1. Engine fits tolerances, and wear limits.

Manufacturers

Design clearances

Component points of measurement

dimensions in

in inches

Allowable

inches

wear or

clearance

Min.

Max.

Min.

Max.

Valve and valve guides.

Intake valves

Cylinder block face-to-guide distance

1-15/32

(3.6717 cm)

Outside diameter

0.6565

0.6575

(1.6412 cm)

(1.6437 cm)

Inside diameter

0.3422

0.3432

0.3447

(0.8555 cm)

(0.8580 cm)

(0.8617 cm)

Valve stem diameter

0.3406

0.3414

0.3386

(0.8515 cm)

(0.8535 cm)

(0.8465 cm)

Step to guide clearance

0.0008

0.0026

0.0046

(0.0020 cm)

(0.0065 cm)

(0.0115 cm)

Valve-to-tappet clearance

0.0140

(0.0350 cm)

Exhaust valves

Cylinder block face-to-guide distance

1.15/32

(3.6717 cm)

Outside diameter

0.6565

0.6575

(1.6412 cm)

(1.6437 cm)

Inside diameter

0.3422

0.3432

0.3447

(0.8555 cm)

(0.8580 cm)

(0.8617 cm)

Valve stem diameter

0.3377

0.3385

0.3357

(0.8442 cm)

(0.8462 cm)

(0.8392 cm)

Stem-to-guide clearance

0.0037

0.0055

0.0075

(0.0092 cm)

(0.0137 cm)

(0.0187 cm)

Valve-to-tappet clearance

0.0160 (Hot)

(0.0400 cm)

0.0170 (Cold)

(0.0425 cm)

Valve tappets

Outside diameter

0.9990

(2.4975 cm)

Tappet bore diameter

1.0000

(2.5000 cm)

Maximum bore-to-tappet clearance

0.0050

(0.0125 cm)

Camshaft and bushings

Bearing journal diameter

No. 1

1.8715

1.8725

1.8705

(4.6787 cm)

(4.6812 cm)

(4.6762 cm)

No. 2

1.8085

1.8095

1.8075

(4.5212 cm)

(4.5237 cm)

(4.5187 cm)

No. 3

1.7457

1.7465

1.7447

(4.3642 cm)

(4.3662 cm)

(4.3617 cm)

4-1