In reply to a message from Alan4d sent Fri 18 Mar 2011:
Alan,
I can assure you that with the head on the bench, a) you
have to raise the head on blocks so that the fully open
valves do not hit the bench and b) you need to turn the
camshafts in unison a few degrees at a time, always in a
clockwise direction, from the TDC #1 cylinder timing
position to avoid the valves on one side clashing with the
valves on the other.
It takes very little effort to bend a valve stem if the
valves clash.
With the head bolted down to the block, you should not
attempt to turn the camshafts individually or in unison
prior to the cam timing being set in relation to TDC #1
cylinder unless you are sure that none of the pistons are
anywhere near TDC on any cylinder.
This is an ‘interference’ engine and valve / piston damage
will occur otherwise.–
The original message included these comments:
Well, that would chill me soemwhat, but I am happy to report that
the inlet camshaft was not THAT difficult to turn and the exhaust
was easy! So I surmise that the valves don’t actually meet on this
model (said he hopefully). If there were valve clashes surely the
reistsnce would be very extreme? I’ve found that Nos 5 and 6 caps
on the inlet were reversed during rebuilding, so maybe that’s been
the problem.
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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