Valves And Seatings - MG MGA Twin Cam Workshop Manual

Fig. A.4 The camshaft housing (sectioned) positioned on a wooden block for valve guide removal
Replacement
When fitting new valve guides they should be pressed in from the top of the cylinder head until the
flange registers on the bottom of the valve spring recess.
A.17 VALVES AND SEATINGS
Grinding and testing
Remove the valves as in Section A.15.
Each valve must be cleaned thoroughly and carefully examined for pitting. Valves in a pitted condition
should be refaced with a suitable grinder or new valves should be fitted.
If valve seats show signs of pitting or unevenness they should be trued using a suitable grinder or
special cutter. When using a cutter care must be exercised to remove only as little metal as is
necessary to ensure a true surface.
When grinding a valve onto its seating the valve face should be smeared lightly with fine- or medium-
grade carborundum paste and then lapped in with a suction grinder (special tool 18G29). Avoid the
use of excessive quantities of grinding paste and see that it remains in the region of the valve seating
only.
A light coil spring placed under the valve head will assist considerably in the process of grinding. The
valve should be ground to its seat with a semi-rotary motion and occasionally allowed to rise by the
pressure of the light coil spring. This assists in spreading the paste evenly over the valve face and
seat. It is necessary to carry out the grinding operation until a dull, even, matt surface, free from
blemish, is produced on the valve seat and valve face.
On completion the valve seat and ports should be cleaned thoroughly with a rag soaked in paraffin
(kerosene), dried, and then thoroughly cleaned by compressed air. The valves should be washed in
paraffin (kerosene) and all traces of grinding paste removed.
After replacing the valves test them by pouring a small quantity of paraffin (kerosene) through the
ports. If there is any leakage of paraffin (kerosene) past the valve seating's the valve should be
removed and examined and, if necessary, reground.
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