4.236 & T4.236 DIESEL ENGINES Section E: Cylinder Head Maintenance Caterpillar

Section E: Cylinder Head Maintenance
1.1. To Remove the Cylinder Head
2.1. To Remove the Valves
3.1. Cleaning
4.1. Valve Guides (Early Engines)
5.1. Valves and Valve Seats
6.1. Hand Grinding
7.1. Valve Seat Inserts
8.1. Skimming of Cylinder Head
9.1. Valve Springs
10.1. Rocker Shaft Assembly
11.1. To Reassemble
12.1. Push Rods
13.1. Valve Stem Oil Seals
14.1. To Re-Assemble the Cylinder Head
15.1. Cylinder Head Gasket
16.1. To Refit the Cylinder Head
17.1. To Check or Adjust Valve Tip Clearances
18.1. Closed Circuit Breather Vent Valve (4.2482 Engines only)


To Remove the Cylinder Head

1. Drain the cooling system.

2. Disconnect battery terminals.

3. Detach the exhaust pipe. Remove turbocharger (T4.236 only).

4. Remove the atomiser leak-off pipe assembly.

5. Remove the fuel pipes from the fuel injection pump outlet and inlet to filter.

6. Disconnect fuel pipe from fuel lift pump outlet to fuel filter. Remove fuel filter.

7. Remove breather assembly.


8. Remove high pressure fuel pipes and atomisers (Fig. E.2).

9. Disconnect fuel pipe and electrical lead at the thermostart.

10. Remove air filter and/or connecting hose. Remove induction and exhaust manifolds.

11. Detach cylinder head cover.


1. Rocker Shaft Bracket

2. Rocker Lever

3. Oil Feed Connection

12. Remove rocker assembly from cylinder head (Fig. E.4). Remove push rods.


13. Remove cylinder head nuts/setscrews in reverse order of tightening sequence shown in Fig. E.12.

14. Remove cylinder head.

To Remove the Valves


Mark all valves with a corresponding mark on the cylinder head to ensure that valves are refitted to their original positions unless replaced with new ones. Earlier engines had their valves and heads numbered during assembly as illustrated in Fig. E.6.


1. Compress spring caps and springs with a suitable valve spring compressor (Fig. E.5) and remove the two half conical collets from each valve.

2. Remove spring caps, springs and valve stem oil seals. Remove valves.


1. Remove all traces of carbon from cylinder head.

2. If the water jacket of the cylinder head shows signs of excessive scale, a proprietary brand of descaling solution should be used.

3. Blank off rocker oil feed oil-way between numbers 2 and 3 cylinders and remove carbon from pistons and cylinder block face.

4. After valve seat machining and valve grinding operations have been carried out, all parts should be thoroughly washed.

Valve Guides (Early Engines)

Engines are fitted with either detachable valve guides or the valve bores are machined direct into the cylinder head.

When wear takes place in the valve bores of cylinder heads without detachable valve guides, valves with oversize stems should be fitted.

Three service valves are available for both inlet and exhaust with oversize stems of 0.003 in, 0.015 in and 0.030 in (0,08, 0,38 and 0,76 mm) respectively.

To fit 0.015 and 0.030 in oversize valves, the bores in the cylinder head must be reamed with a piloted reamer. Suitable reamers for carrying out this operation can be obtained from Messrs. V. L. Churchill and Co. Ltd. (see Appendix).

Where detachable valve guides are fitted, these can be replaced.

To fit new guides; clean the parent bore, smear the outer surface of the guide with clean oil and press home the guide until 0.625 in (15,87 mm) is protruding above the cylinder head. The guides are manufactured from cast iron and are brittle.

Valves and Valve Seats

Check the valve stems for wear and their fit in the guides.

Examine the valve faces for pitting or distortion. Valve refacing should be at an angle of 45° or 30° for inlet valves on T4.236 engines (see Page B.10).

Valves should always be refitted to their original seats and any new valve fitted should be suitably marked to identify its position if removed at a later date. Refer to Fig. E.6. for illustration of valve numbering.

Note current exhaust valve depths on Page B.10 became effective from the following engine numbers:-


Where it is necessary to conform with the smoke density regulation B.S.AU 141a: 1971, then valve depths must not exceed production limits as given on Page B.10. See Fig. E.7.

The maximum wear limits quoted on Page B.3 are for areas in which the smoke density regulation do not apply.

The valve seats in the cylinder head should be reconditioned by means of cutters or specialised grinding equipment, at an angle of 45° or 30° for inlet valves on T4.236 engines. Suitable valve seat cutters for 45° seats are included in kit 21825064 (see Appendix) and these cutters give a differential valve seat to reduce the width of the valve seat. A special cutter 21825065 is required for 30° valve seats.

As narrow a seat as possible should always be maintained.

Hand Grinding

When grinding in valves it is essential that no signs of pitting are left on the seatings. At the same time care should be taken to avoid unnecessary grinding away of the seat.


After grinding operations have been completed, check the valve head depths relative to the cylinder head face (Fig. E.7) and wash the cylinder head.

Valve Seat Inserts

In the majority of applications, valve seat inserts are not fitted to production engines, but may be fitted in service with the exception of T4.236 inlet valves which have a 30° seat.

However, there are some 4.248 and T4.236 applications in which exhaust valve seat inserts are fitted in production and where it is thought necessary, they may be replaced by new ones.

When fitting inserts to the valve seat, ensure that genuine Perkins Parts are used and proceed as follows: follows:

a) For cylinder heads having removable valve guides, press out existing guide and clean the parent bore. Press in new guide.

b) For guideless cylinder heads.

Using the appropriate oversize piloted reamer-0.015 in (0,38 mm) or 0.030 in (0,76 mm) according to the condition of the valve bores in the cylinder head-ream out the valve stem bores.

NOTE: Appropriate oversize stem replacement valves will be needed when this operation has been carried out on guideless cylinder heads.

Proceed as follows for either type cylinder head, with or without valve guides:-

E8 Inlet A-0.283/0.288 in (7,19/7,31 mm) B-2.0165/2.0175 in (51,22/51,24 mm) C-Radius 0.015 in (0,38 mm) max. Exhaust A-0.375/0.380 in (9,52/9,65 mm) B-1.678/1.679 in (42,62/42,64 mm) C-Radius 0.015 in (0,38 mm) max.

1. Using the new valve bore as a pilot, machine the recess in the cylinder head face to the dimension in Fig. E.8.

E9 Inlet A-1/16 in (1,59 mm) at 45° B-3/4 in (19,05 mm) C-0.250 in (6,35 mm) D-3 in (76,20 mm) E-1.582/1.583 in (40,18/40,21 mm) F-2.009/2.019 in (51,03/51,28 mm) G-1/32 in (0,79 mm) radius H-1/16 in (1,59 mm) radius J-1/16 in (1,59 mm) at 45° K-0.372/0.373 in (9,45/9,47 mm) Exhaust A-1/16 in (1,59 mm) at 45° B-3/4 in (19,05 mm) C-0.312 in (7,92 mm) D-3.0 in (76,20 mm) E-1.248/1.249 in (31,70/31,72 mm) F-1.670/1.680 in (43,42/43,67 mm) G-1/32 in (0,79 mm) radius H-1/16 in (1,59 mm) radius J-1/16 in (1,59 mm) at 45° K-0.372/0.373 in (9,45/9,47 mm)

2. Remove all machining swarf and clean the insert recess. Using the valve bore as a pilot, press the insert home using the inserting tool (Fig. E.9). Under no circumstances should the insert be hammered in, neither should lubrication be used during pressing in.

3. Inspect to ensure that the insert has been pressed fully home and is flush with the bottom of the recess.

E10 - 4.2482,4.248, 4.236 and 4.212 engines only.
Showing Flare to be cut at 30°
Dimension A
0.094 to 0.099 in (2,39 to 2,51 mm) for exhaust valve
0.100 to 0.105 in (2,54 to 2,67 mm) for inlet valve.

4. Using the valve bore as a pilot, machine the "flare" to the dimensions in Fig. E.10.

5. Remove all machining swarf and burrs.

6. Re-cut the valve seat at an included angle of 90°, so that the valve head depth below the cylinder head face is within the production limits 0.047/0.057 in (1,19/1,45 mm) for exhaust valves and 0.035/0.045 in (0,89/1,14 mm) for inlet valves.

NOTE: Work as closely as possible to the minimum figure to allow for re-seating at a later date. When refacing a valve the included angle of the contact face is 90°.

If the cylinder head face has been skimmed since the fitting of valve seat inserts, then the following is allowed:-

a) Machine to the dimensions given in Fig. E.10 and continue as in stages 5 and 6.

b) If the insert is damaged or unserviceable through wear, it must be removed and replaced with a new one. Before fitting, however, the back of the insert should be surface ground, removing sufficient material to give a flush fitting. Do not forget to rechamfer the insert as it was prior to grinding, i.e. 0.020/0.030 in (0,508/0,762 mm) at 45°. Then proceed as in stages 2 - 6.

Skimming of Cylinder Head

A maximum of 0.012 in (0,30 mm) may be removed providing the nozzle protrusion is not greater than 0.175 in (4,44 mm). This figure must not be obtained by the use of additional washers to the atomisers

Ensure that the valve depths are within the limits quoted on Page B.3 or on Page B.10.

Valve Springs

A new set of valve springs should always be fitted every major overhaul. Either one or two valve springs are fitted according to application/engine type.

Examine the valve springs with regard to squareness of ends and pressures developed at specified lengths, details of which can be found in "Technical Data", page B.10.

Where springs incorporate damper coils at one end, these must be fitted towards the cylinder head.

Rocker Shaft Assembly

To Dismantle:-

1. Remove circlips and washers from each end of the rocker shaft.

2. Withdraw the rocker levers, springs and support brackets.

3. Remove the locating screw from the rocker oil feed connection and withdraw the connection. Examine the rocker lever bores and shaft for wear. Rockers should be an easy fit on the shaft without excessive side play.

To Reassemble

1. Fit oil feed connection to rocker shaft and secure with the locating screw, ensuring that the screw enters the locating hole in the shaft.

2. Refit the support brackets, springs, and rocker levers in the correct order (Fig. E.4). The support brackets are interchangeable and when fitting them ensure that the securing stud/setscrew holes are to the right viewing the shaft from the front end, with each pair of rockers inclined away from each other at the valve end.

3. Fit securing washer and circlip to each end of the shaft.

Push Rods

Check the push rods for straightness. If any are bent, fit replacements.

Valve Stem Oil Seals

Where oversize valves are fitted, always ensure that correct size valve seals or 'O' rings are used.


1. Collets

2. Valve Spring Cap

3. Oil Deflector

4. Inner Valve Spring

5. Outer Valve Spring

6. Valve Spring Seat

7. Exhaust Valve

8. Inlet Valve

All hydraulically governed engines and certain mechanically governed engines have rubber oil deflectors fitted to inlet valve stems only (see Fig. E.3). When fitting these oil deflectors, the open end should be towards the cylinder head.

With the majority of mechanically governed engines, oil seals are fitted to both inlet and exhaust valves. Earlier engines had a shallow rubber oil deflector fitted to the valve stems and positioned above the conical valve spring seating collar, the open end of the deflector being fitted towards the cylinder head. Later engines have a thin valve spring seating washer and a rubber oil seal which fits over the integral valve guide protrusion. In some cases, this latter seal has a nylon insert. The later sealing arrangement, due to a change in the diameter of the valve guide protrusion, is not interchangeable with the earlier sealing arrangement.

On some engines, the seals are manufactured from Viton or silicon rubber material and they have a garter spring fitted around their outer circumference.

In manufacturing, some engines have a red coloured material for inlet valve seals and black for exhaust valve seals. The red seal may only be fitted over the inlet valve. It is unsuitable for exhaust valves but the black seal may be fitted to either exhaust or inlet.

The 4.2482 engine has a valve stem oil seal on both inlet and exhaust valves. The seals have garter springs round the seal neck for improved oil control.

To Re-Assemble the Cylinder Head

1. Lightly oil valve stems.

2. Fit valve to its correct guide or bore.

3. Fit valve stem oil seals.

4. Locate spring seat washers, valve springs and spring caps in position.

5. Compress each valve spring and fit the valve collets.

E11, Valve Cap Sealing Arrangement

NOTE: As from Engine No. LD-----U778518H, 'O' ring seals have been fitted in the valve spring caps under the collets. The valve spring caps have been changed which have a deeper body so that the seal can be fitted as shown in Fig. E.11. The new caps are fitted to both valves, but the seals are fitted to exhaust valves only. T4.236 engines have two 'O' rings fitted in each valve spring cap.

Cylinder Head Gasket

Always use a new cylinder head gasket.

Cylinder lines must be fitted to give a protrusion of 0.028/0.037 in (0,71/0,94 mm) above the cylinder block face. On early 4.236 engines, liners were fitted as described on Page G.2.

Where two studs are used for gasket location purposes, these must be fitted at the end positionsof the left hand row of tappings, positions 19 and 22, Fig. E.12.

Ensure that the correct replacement gasket is fitted with either jointing compound or dry, depending on the gasket type. They should be fitted as follows:-

The cylinder heads of all engines fitted with these gasket types must be tightened down to the correct torque after initial warm-up and again when the vehicle or machine has completed 500/1,000 miles (800/1600 km) or 25/50 hours service (not necessary for 4,2482 engines). See the following subsection for further cylinder head refitment details.

To Refit the Cylinder Head

Ensure that the rocker assembly oil feed passage in the cylinder head is free from obstruction. When refitting the cylinder head a new gasket should be used.

1. Lightly oil threads and tighten the nuts/setscrews progressively (in 3 stages) in the order shown in Fig. E. 12, to a torque of 60 lbf ft (8,5 kgf m) or 81 Nm for 7/16 in studs or 100 lbf ft (13,8 kgf m) or 136 Nm for 1/2 in studs/setscrews.


2. Fit the push rods and refit the rocker shaft assembly. Fit a new rubber sealing ring to the rocker oil feed connection.

With old type rocker oil feed connection, fit the new seal immediately below the lower convolution, so that when the pipe is inserted into the cylinder head, the "O" ring will roll up and over the lower convolution and locate itself correctly between the two convolutions (Fig. E.13).

With the latest type rocker oil feed connection, the rubber olive should be fitted in the recess in the cylinder head, before fitting the rocker shaft assembly.

3. Adjust the valve clearances, as detailed later. Fit the rocker cover.

4. Refit atomisers with new copper sealing washers ensuring that they seat squarely. Refit the high pressure fuel pipes (see Pages N.10 and N.11).

NOTE: Current atomisers are fitted with a spacer and rubber dust seal. The dust seal must always be renewed and fitted below the spacer.

5. Fit the breather pipe assembly to the cylinder head cover.

6. Refit the fuel filter to the cylinder head and the fuel pipe between the lift pump outlet and the filter.

7. Fit the fuel pipes between the filter and the injection pump inlet and outlet.

8. Refit the atomiser leak-off pipe assembly.

9. Refit inlet and exhaust manifolds. Manifold joints with an identification notch or square shoulder, must be fitted with the notch or square shoulder to the top of the manifold. Where corrugated type joints are used, they must be fitted without jointing compound.

10. Connect the exhaust pipe.

11. Refit the air filter and connections. Fit the water outlet hose. Re-connect the battery terminals.

12. Fill the cooling system and check for water leaks.

13. Bleed the air from the fuel system as detailed on Page N.9.

14. Run the engine until normal operating temperature is attained and retighten the cylinder head nuts/setscrews, in sequence, to the torque given on Page B.2.

NOTE: When retightening cylinder head nuts/setscrews, the engine coolant outlet temperature should not be less than 170°F (77°C).

If the nut/setscrew moves when retightening, then tighten up to the torque quoted on Page B.2.

If the nut/setscrew does not move before the correct torque is achieved, then slacken off 1/12 to 1/6 of a turn (30° to 60°) and retighten to the correct figure. After retightening all the nuts/setscrews, the first 10 positions should be rechecked without further slackening off to ascertain they are still tightened to the torque quoted.

15. Reset the valve clearances, as detailed below. Fit the rocker cover.

The 4.2482 engine cylinder head cover is fastened in position with a controlled pressure on the joint to give a positive seal. The cover is fastened down onto the rocker assembly retaining extension nuts and is kept in position by a rubber seal and steel washer fastened between the cylinder head cover and cover retaining setscrews. The rubber sealing washer must be positioned with the radiused edge downwards.

NOTE: Except for 4.2482 the cylinder head should be tightened down to the correct torque in the correct sequence after the vehicle or machine has completed 500/1,000 miles (800/1600 km) (25/50 hours) service.

To Check or Adjust Valve Tip Clearances


These are checked between the top of the valve stem and rocker arm (Fig. E.14) and should be 0.012 in (0,3 mm) with the engine cold.

When adjusting valve clearances the following procedure should be adopted:-

1. With the valves rocking on No. 4 cylinder (i.e., the period between the opening of the inlet valve and the closing of the exhaust valve), set the valve clearances on No. 1 cylinder.

2. With the valves rocking on No. 2 cylinder, set the valve clearances on No. 3 cylinder.

3. With the valves rocking on No. 1 cylinder, set the valve clearances on No. 4 cylinder.

4. With the valves rocking on No. 3 cylinder, set the valve clearances on No. 2 cylinder.

Closed Circuit Breather Vent Valve (4.2482 Engines only)


This is fitted between the cylinder head cover and induction manifold (Fig. E.15).

To clean, seal the small breather hole in the top face and wash the unit in gasolene or kerosene. If air pressure is used to dry the unit, you must only use low pressure, because high pressure will damage the unit.