MG MGA Twin Cam Workshop Manual page 33

A
THE ENGlNE
Section A. ll
CA. \ tSIIAFlS
Remo,.., the camshaft co\'ers and disconnect the
cam-
shaft driving sproclcets (see Section A. lO). Slru:ken the
camshaft bearing cap nuts a turn at a time to allow the
camshaft to rise evenly on the studs. Commence at the
rear bearing and work towards the front. If this is not
done the canuhaft thrust Oange may
cause damage to
its housing or the camshaft may suffer distonion or
breakage.
Before replacing the camshaft set the crankshaft to
90" B.T.D.C. on No. 1 cylinder to obviate an open valve
fouling a piston crown. Position the camshaft with the
timing slots in the cap and shaft approximately in line.
Tighten the bearing cap nuts a tum at a time. commenc-
ing with the froat bearing. to fit the camshaft e\'enly and
to prevent the thrust flange fouling the thrust slot. Finally
tighten the nuts to the torque loading
figures
given in
' GEI'I<"ERAL DAT A'.
The camshaft bearing
caps
are marked, and care must
be taken to replace them in their correct positions. After
assembly check and adjust the valve timing (Section A. 19).
Section A.12
CAMSHAFf BEARINGS
Each camshaft runs in three non-adjustable white-metal
shell bearings.
To renew the bearings disconnect the camshaft driving
sprockets and remove the camshafts (sec Section A. II),
when the bearings may be extracted.
Care should be exercised to see that the bearing
journals, cte., are tltroughly cleaned before installing
new
bearings. No scraping is required, as the bearings
ate
machined during manufacture to give the correct
diametrical clearance.
Section A.l3
CYLINDER HEAD
Remon)
D rain the cooling system and remove the header tank,
thermostat housing, and exhaust manifolds as detailed in
Section A.9. Remove the air cleaners and carburetters
as
descnDed in Section A .S.
Un-ew
the cyliocler bead
oil feed pipe at the right-hand rear of the bead.
Remo\'e the two bolts, spring washers, and plain
washers securing the cylinder head water intake pipe a t
the rear of the bead.
Detach the high-tension cables and remove the sparking
plugs, taking care not to damage the porcelain insulators.
R~mo,..,
the camshaft covers and disconnect
th~
cam-
shafts from their driving sprockets<- Section A.JO).
A.6
R~move
the 10 cylinder bead retaining nuts and the
cylinder head. When lifting the bead a direct pull should
be gi\-en to withdraw it evenly up the studs..
R~p.beemeat
When refitting the cylinder bead it is advisable to use
a new gasket. The seals 61led between the
front camshaft
bearings and the engine front plate should be examined,
and renewed
if
necessary.
Tighten the cylinder bead nuts in the correct sequence
(see
Fig. A.3), using a torque wrench. T he torque
wrench settings are given in the 'GENERAL DATA'
section.
Reassembly continues in the re\'efSC order to the
dismantling procedure. After final tightening or the
cylinder head nuts ebeclc the valve clearances, and adjust
if necessary (see Section A.l8).
Fig. A .3
Th~ corre~t
order of tfghUning ond
sla~kenlng
the
cylinder head rout.r
Section
A.14
DECARBONIZING
Remove the cylinder bead
as
described in Section
A.13.
Withdraw the valves
as
described in Section A. IS.
Remove the cylinder bead gasket and plug the water-
ways with
a
clean
rag..
If
special equipment is not available for decarbonizing
it
will
be necessary to scrape the carbon deposit from
the piston crowns and cylinder bead, using a blunt
scraper.
A ring of carbon should be left round the periphery
of the piston crown and the rim of carbon round the
top of the cylinder bore should not be touched. To
MGA
(Twin
Cam.) muc
J. 2n6S