Triumph TR7 Owner's Manual page 46

(6) Take great care when fitting spark plugs not to cross-
thread the plug, otherwise costly damage to the
cylinder head will result.
(7)
Tighten .the plugs just sufficient to ensure a leakproof
jOint with the cylinder head.
00 NOT OVERTIGHTEN
(8) When fitting the leads to the plugs ensure that the
shrouds are firmly seated on the plugs
It
is imponant
that only the specified spark plugs are used
for replacements. See General Specification,
Incorrect grades of plug may lead to piston over-heating and
engine failure.
Check Security of Distributor Vacuum Line and
Operation of Vacuum Unit
Check Ignition Wiring (including electric fuel pump
wiring) for security, fraying. chaffing and deterioration
MAINTENANCE AND ADJUSTMENTS
Fig.20 Spark plug gap sBtting tool
45