| Intake
and exhaust valve guides in Chevrolet 396 and 427 CID engines
appear to be of the normal removable types, however, in OEM
production undrilled guides are installed and finish-bored by
gun drilling, locating from the valve seat which results in
seat-to-guide ID concentricity. Since in production the valve
guide receiving bores are not located in the same manner a lack
of concentricity between the ID and OD of the guide exists.
Worn valve guide ID's can be
restored by methods employed when reconditioning integral
guides. Valves with oversize stems are available from replacement
sources. |
|
There are also
concentric intake and exhaust guides available from replacement
manufacturers, however, members are warned to be cautious when
installing them. Valve seats might have to be installed to reestablish
seat-to-guide alignment. Further, the exhaust guide is water-cooled,
intersecting the water jacket. The OD of the guide consists
of two different diameters. Since the diameter on the rocker
arm end of the valve guide is larger, the guide must be removed
by driving it away from the seat out of the top side of the
cylinder head and must be installed from the top side. If this
procedure is not followed, the cylinder head will be damaged,
resulting in coolant leakage. |
