Cylinder Head - BMW 5251 Service Manual

11 6-5
I
Cylinder Head and valvetrain1
4
Timing chain tensioner bracket (V-8)
(Tool No. BMW 11
7
380)
CYLINDER HEAD
This section provides the specifications and special recondi-
tioning information necessary to repair the cylinder heads
covered by this manual.
The disassembled cylinder head should be inspected for
warpage and cracks. Check the valve guides and valve seats
for wear before machining a warped head. Always decarbon-
ize and clean the head before inspecting it.
Visually inspect the cylinder head for craclts. If a cracked cyl-
inder head is suspected and no craclts are detected through
the visual Inspection, have the head further tested for cracks
by an authorized BMW dealer or an ASE certified machinist.
A cracked cylinder head must be replaced.
NOJE-
When disassembling and inspecting the cylinder head, be
sure to checlc the camshaft carrier bearing surfaces using a
straight edge for warpage, and check the lifter bores for wear.
A high-quality straight edge can be used to checlc for
warpage. A warpage of 0.05 mm (0.002 in.) is acceptable
without machining. A warped cylinder head can be machined
provided no more than 0.3 mm (0.012 in.) of material is re-
moved. If further machining is required, the head should be
replaced. Removing more than this amount will reduce the
size of the combustion chamber and adversely affect engine
performance. A 0.3 mm thicker head gasket for machined
heads is available from an authorized BMW parts depart-
ment.