In the middle of the part number on the head is a two digit code --
the original is -14-. the first improved head is -17- and the best
version is the -22- one.
They crack through from the combustion chamber to the coolant and or
oil passages, causing the usual results -- overheating, coolant use,
etc.
The head gaskets also fail pretty often, between cylinders and from
cooling passages or oil return to the outside, resulting in leaks.
Worst failure is between the oil passage across the front of the
block -- failure here allows oil to enter the #1 cylinder under
pressure. If enough gets in there, the #1 rod gets bent.
All the bits from the -14- head will fit the -22-, with the proviso
that it may be necessary to machine the pre-chambers to clear the
bottom of the large hole in the heads. The correct ones, with
inclined injectors, are a bit shorter at the shoulder, and if they
don't fit correctly the pre-chamber will leak compression at the
upper seal, usually badly enough that the engine will not run.
Always use all new head bolts, they often fail when re-used, as I
discovered on my old 300D.
Peter
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