SAFARI

ENGINE

Fig. 14

Fig. 15

Fig. 16

REMOVAL OF VALVE SEAT INSERTS

For both inlet and exhaust valves, valve seat inserts

are standard fitment. They are shrunk and then

pressed in cylinder head. Therefore, removal of valve

seat inserts should be done only if they are damaged

beyond repair or worn out beyond specified limits.

1 For removing seat inserts from cylinder head, use

suitable boringmachine. Bore old insert thin (about

0.5 mm thickness) and then try it out.

2 Alternatively, use a suitable turning tool to cut an

angular groove into seat insert and then pull it

out with a suitable puller. In order to avoid

damaging of machined cylinder head parting

surface, place copper or any other protective

sheet-metal under puller supports.

3 Measure basic bores for valve seat inserts with

bore gauge. If the boring and prying is done

carefully without damaging the parent bore of

the inserts, fitment of an oversize insert will

normally be not necessary. However, if the parent

bore dimensions deviate from the values

specified, enlarge bore to the next repair size. This

should done on a suitable fine boring machine.

4 Re-machined bore must exactly be at right angles

to the cylinder head surface and the bore size

should be strictly within specifications so as to

ensure proper interference fit of the inserts.

5 Clean basic bores in cylinder head and seat inserts

thoroughly before fitting.

INSTALLATION OF VALVE SEAT INSERTS

1 Place valve seat inserts in liquid oxygen for about

20 to 30 minutes to bring their temperature down

to - 195 deg C (when liquid oxygen stops no longer

producing 'vapour' and stops spurting, valve seat

inserts have a temperature of approximately - 195

deg C). If liquid oxygen is not available, keep

inserts in ice and salt mixture for about 6-8 hours.

CAUTION

Do not touch liquid oxygen or chilled valve seat

inserts with your fingers. Use a pair of tongs.

2 Heat cylinder head to approx. 80 deg C in a water

bath.

3 Take seat inserts out of liquid oxygen by using

tongs and place on bore of heated cylinder head

(Fig. 15). Install them quickly by slight hammering

with the help of a drift. Fig. 16.

4 After inserting seat inserts, check distance

between parting surface of cylinder head and

face of valve seat insert. If necessary, re-machine

the face with an end mill/suitable cutter.

5 Machine valve seats as per specifications.