I wonder if the valves do actually rotate when the engine
runs ?
In my case the shafts were all badly worn on one side of
the motor, so I think they actually do NOT rotate and thus
wear faster then must-be.
The valve stems only have one groove, and the small
retainers were all stuck, at least one of every pair was so
frozen I had to use a small hammer to whacken them out of
the valve collar.
Is this normal ?
Where later XK engines improved on this issue ? Mine is
1966 4.2.
And, being on this subject, shall I keep the oil pump ? I
will measure it for wear, but it does not look too bad.
Carsten–
Restoration in progress: 1966 2+2 LHD manual
Goettingen, Germany
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Carsten sent Sat 15 Jun 2013:
I don’t know any engine where the valves rotate. What would
motivate them to do so? They are securely clamped to the
springs by the split keepers, and the springs certainly do not
rotate.–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Pete55Tbird sent Sat 15 Jun 2013:
Search the topic on J-L for the last 3 months - there was
a discussion on one of the engine forums - V12 I think.
Could even have heen the last month. Rotation is normal
but possibly once wear sets in they may tend to cant over
fractionally a stop rotating, which may concentrate wear?
Pete–
1E75339 66 D, 885958 62 FHC,1R27190+1R28009 70FHCs, 1960 Mk9
Gaithersburg, Maryland, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Carsten sent Sat 15 Jun 2013:
Which side had the stuck valve keepers? Exhaust side? If
they’re stuck to the valves, and guide wear is severe
(especially on the exhaust side), I doubt there was much oil
up top. I think you may find a plugged oil passage or Y-pipe.–
The original message included these comments:
In my case the shafts were all badly worn on one side of
the motor, so I think they actually do NOT rotate and thus
wear faster then must-be.
The valve stems only have one groove, and the small
retainers were all stuck, at least one of every pair was so
frozen I had to use a small hammer to whacken them out of
the valve collar.
Is this normal ?
Where later XK engines improved on this issue ? Mine is
1966 4.2.
And, being on this subject, shall I keep the oil pump ? I
–
Pete Peterson 70E(193K) XJ40s(88-270K,89-97K, 94-122K)
Severna Park, Maryland, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Ray Livingston sent Sat 15 Jun 2013:
As mentioned, they do passively rotate–not driven by
rotation of the cam follower nor by asymmetry of gas flow
past them (at least not primarily).
I was reminded of the reason last week when my garage door
torsion spring failed. Instructions pointed out that the
springs lengthen when twisted in one direction and shorten
when twisted in the other–don’t preload the spring the
wrong way. Thanks to the beautiful symmetry of physics, the
converse is true as well…compressing a spring rotates it
in one direction, and allowing it to expand rotates it in
the other. True–it’s about the same both ways. But not
exactly due to some higher order inertial considerations
attributable to the fact that that only one end of the
spring is compressed relative to the spring’s center of
mass. Don’t really understand that part very well. But
there’s a net rotation, and the force involved increases
non-linearly with RPMs (inertial forces get bigger faster).
If you don’t want your springs to rotate, just buy special
springs
I vaguely remember there was a military version of the XK which had a
mechanism to cause the valves to rotate.
Mike Frank
At 04:18 PM 6/15/2013, you wrote:>In reply to a message from Carsten sent Sat 15 Jun 2013:
I don’t know any engine where the valves rotate. What would
motivate them to do so? They are securely clamped to the
springs by the split keepers, and the springs certainly do not
rotate.
In reply to a message from Robert Wilkinson sent Sat 15 Jun 2013:
Really nice explanation Bob. Makes a lot of sense to me.
Carsten - as far as sticking collets is concerned, I often
find it necessary to give the spring compressor a sharp tap to
loosen them once the springs are compressed. Certainly not a
whack with a hammer but just enough to loosen them. Even if
the valve/spring rotates, I suppose the collets stay pretty
fixed in the keeper which causes them to stick over time.–
Neville - http://www.XJ13.eu, XJ13 in-progress 1962 3.4 MK2
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Carsten sent Sat 15 Jun 2013:
Hi Carsten - yes, you should certainly measure the
clearances as shown in the Haynes Manual (or similar). Also,
pull out the gears and check to see they are undamaged with
no sign of excessive scoring or grooves. They should turn
freely with no signs of binding or looseness of their
shafts. If all is well and within tolerance, I would
personally re-use the pump. Your gasket kit should include
new ‘‘O’’ rings and it is important to ensure there is a good
seal between the oil deliver/suction pipes and the pump when
you get round to re-installing it.
If you need to replace it, I do recommend buying an uprated
version. They don’t cost much more and are supplied by most
of the usual suspects.–
The original message included these comments:
And, being on this subject, shall I keep the oil pump ? I
will measure it for wear, but it does not look too bad.
In reply to a message from V12 Racer sent Sat 15 Jun 2013:
Hi Neville,
I did pull the rotor and the outer part. It looked a bit
like a Wankel engine to me :-).
Yes, no scores. All the parts I found in the sump where
larger, like the tensioner and one of the camshaft wheel
bolts (no saftey wire was used !), so nothing bad like
Chris Rooke found…
Will measure and probably re-use as you said.
Carsten–
Restoration in progress: 1966 2+2 LHD manual
Goettingen, Germany
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Michael Frank sent Sat 15 Jun 2013:
Yes, the military had positive rotation to help with valve
wear on very poor fuel and therefore avoid potentially
rapid deterioration in the field. With positive rotation
it happens even at very slow speed whereas passive
rotation happens more markedly with revs. I saw a strobe
video years ago of an OHV pushron/rocker engine and you
could see the valves slowly move around withe the valve,
keeper and springs all moving as one unit IIRC. The
relative motion was between the lower spring seat and the
head I think. It’s all in the recent thread elsewhere.
Pete
Pete–
1E75339 66 D, 885958 62 FHC,1R27190+1R28009 70FHCs, 1960 Mk9
Gaithersburg, Maryland, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
