CHAPTER 4. BASIC ENGINE OVERHAUL - TM-5-4320-259-340021

CHAPTER 4

BASIC ENGINE OVERHAUL

Section I.

INTRODUCTION AND FITS, TOLERANCES

AND WEAR LIMITS

all other information relating to engine overhaul.

4-1. Introduction

Paragraph 4-2 provides the fits, tolerances, and

This chapter provides instructions relating to

allowable wear limits which are useful in deter-

engine repair and overhaul. It includes information

mining if parts replacement is necessary.

regarding disassembly, inspection of parts to

4-2. Engine Fits, Tolerances, and Wear Limits

determine if their. continued serviceability is

Table 4-1 lists the fits and tolerances applicable to

possible or if they should be replaced, instructions

the engine. Refer to the table to determine if parts

covering repair techniques such as valve grinding

r e p l a c e m e n t is required or if continued serv-

and cylinder honing, reassembly and tolerance

iceability of the parts is possible.

checking to assure proper fits and clearances, and

Table 4-1. Engine Fits, Tolerances, and Wear Limits

Dimension (in.)

Item

2 3/8 x 2

Bore and stroke

2.375

Bore diameter, new

0.0038/0.0228

Crankshaft end play

0.9360/0.9355

Crankshaft-connecting rod journal size

0.0050/0.0160

Crankpin-connecting rod side clearance

0.8750

Crankpin length

0.9840

Main bearing journal diameter, new

0.0010/0.0025

Connecting rod to crankpin running clearance

0.0005/0.0010

Connecting rod to piston pin clearance

0.0002 Int. to

Piston pin to piston boss

0.0002 Loose

0.0030/0.0040

Piston to cylinder bore (thrust face)

0.0035/0.0060

Piston to cylinder bore (top of skirt)

0.51632

Piston pin bore size

0.5620

Piston pin diameter

0.0020/0.0040

Ring side clearance, top ring

0.0020/0.0040

Ring side clearance, middle ring

0.0015/0.0035

Ring side clearance, oil ring

0.0070/0.0170

Ring end gap

0.0930

Ring width, inches, top ring

0.0930

Ring width, inches, middle ring

0.1870

Ring width, inches, oil ring

0.0010/0.0025

Camshaft pin to camshaft clearance

0.0005/0.0012

Camshaft pin to block (bearing plate end)

0.0055/0.0020

Camshaft pin to block (P. T. O. end) (interference)

0.0010/0.0025

Camshaft pin to breaker cam

0.0050/0.0200

Camshaft end play

0.0005/0.0020

Valve stem clearance in guide, intake

0.0020/0.0035

Valve stem clearance in guide, exhaust

0.0020/0.0050

Valve seat in block, exhaust (interference)

0.0050/0.0090

Valve clearance, intake (cold)

0.0110/0.0150

Valve clearance, exhaust (cold)

0.9790/0.9890

Valve head diameter, intake

0.8070/0.8170

Valve head diameter, exhaust

44.5 degrees

Valve seat angle

degrees

Valve face angle

0.0370/0.0450

Valve seat width

0.0005/0.0020

Valve tappet clearance in block

0.0012/0.0027

Governor bushing to governor cross shaft clear

0.0007/0.0022

Ball bearing to cylinder block (interference)

4-1