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#Post#: 2491--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: banquo Date: October 19, 2018, 5:04 pm
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Mine doesn't smoke or use oil, but then it also has new valve
guides and oil seals on them too....
#Post#: 2492--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: Dunders Date: October 20, 2018, 9:43 am
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I'm only going to do that when I *have* to. Or this winter, if
I run out of other things to do. Not likely.... SWMBO can
always find me things to do:-(
#Post#: 2569--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: JamesNFalconaut Date: March 10, 2019, 4:56 am
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It bares repeating Banquo, your write-up and pics are proving
very useful.
Thanks!
#Post#: 2570--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: banquo Date: March 10, 2019, 6:26 am
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[quote author=JamesNFalconaut link=topic=360.msg2569#msg2569
date=1552211760]
It bares repeating Banquo, your write-up and pics are proving
very useful.
Thanks![/quote]
Glad it's been useful; makes it all worthwhile, and the whole
point of this is that we all help each other out 8)
#Post#: 2576--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: cloggy Date: March 15, 2019, 5:08 pm
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"I discovered significant wear in the valve guides (and I
believe that this is a precursor to stuck valves and
catastrophic failure, as we never hear of dropped valves on new
or recently rebuilt engines)"
Not sure why you've said this banquo since you were in on
another conversation in which a forum member replaced his
valves with thin stemmed examples and promptly had the brand new
plot drop another valve. Or perhaps you've forgotten? He came to
the conclusion that tappets gaps or rather lack of were the
cause. One size of the volkswagon flat four Beetle engine was
also known to do this in the very late 60s early 70s, To rid
themselves of the problem Volkswagon changed valve clearances
from .004mm to .006mm. NLM used to set their valves to no gap
whch seems ok as long as the engines aren't worked hard, but
continental advice has always been that the valves are fine as
long as the valve clearances are correct. Since these engines
have very heavy valve gear and the engine unshrouded by the fuel
tank, the tendancy is to run them tight to quieten the valve
gear, Big mistake, standard these engines should always sound
very tappety, somewhere between an industrial sewng machine and
a concrete mixer..... with gaps set at .010 and .0.20mm
respectively for inlet and exhaust cold engine I think. Perhaps
you can advise?
#Post#: 2578--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: banquo Date: March 16, 2019, 6:48 am
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[quote author=cloggy link=topic=360.msg2576#msg2576
date=1552687712]Not sure why you've said this banquo since you
were in on another conversation in which a forum member
replaced his valves with thin stemmed examples and promptly had
the brand new plot drop another valve. Or perhaps you've
forgotten? He came to the conclusion that tappets gaps or rather
lack of were the cause. One size of the volkswagon flat four
Beetle engine was also known to do this in the very late 60s
early 70s, To rid themselves of the problem Volkswagon changed
valve clearances from .004mm to .006mm. NLM used to set their
valves to no gap whch seems ok as long as the engines aren't
worked hard, but continental advice has always been that the
valves are fine as long as the valve clearances are correct.
Since these engines have very heavy valve gear and the engine
unshrouded by the fuel tank, the tendency is to run them tight
to quieten the valve gear, Big mistake, standard these engines
should always sound very tappety, somewhere between an
industrial sewing machine and a concrete mixer..... with gaps
set at .010 and .0.20mm respectively for inlet and exhaust cold
engine I think. Perhaps you can advise?
[/quote]
Memory's not what it used to be Cloggy; I do remember someone
(Huub) saying he's dropped a valve after an 8mm conversion, but
don't recall it being on a new rebuild. I don't see valve
clearance being related to the problem. M-G show two different
clearances, 0.05-0.10 and 0.10-0.20. The tight clearance is much
quieter but I've found a loss of compression on a hot engine,
and reverted to the larger clearances. My theory, FWIW, is that
excessive guide wear allows the valve stem to tilt far enough to
jam in the guide, preventing closure, and with the inevitable
collision with the piston following. If it were related to
clearances, surely the problem would occur immediately, but
certainly most of the issues I've heard of occurred after
significant mileage. The stock valve springs seem ridiculously
heavy, resulting in excessive camshaft wear, and my guess is the
Mandello beefed them up in an unsuccessful attempt to overcome a
known issue with dropped valves? Just a guess, and I'm no
expert... ;)
#Post#: 2591--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: cloggy Date: March 20, 2019, 4:56 am
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Huub's engine was low miieage when the valve broke, with no wear
or galling on the valve stem. My theory, recently given more
weight by the volkswagon experience is thus.
The pushrods are massive. As the engine heats up they are slow
to warm [I've noticed tappet noise goes up and then drops back
as the engine warms]. As the engine cools down they are the last
to cool. Thus the need to run big clearences. If the tappets
are too tight both the valve seat and the valve have flame
constantly over their surface. The seat thus can warp or be
forced/drop out by expansion and the valve stem gets very hot
causing the metal to lose strength. Thus when the valve cools
down sufficiently to hit the seat again it can then break. Huub
came to the understanding that the clearances were crucial, even
with lighter valves and springs. Loads of old hands in Europe
say the same. Keep an eye on the valve clearances and the
engines will run and run.
I guess the cam doesn't incorporate quietening ramps [or it may
just be the disparate metals neccessatating large clearances]
so the valve does get far more of a hammering than say my M21
whch will happily glow in the dark and still not break a valve
with it's soft springs. The volkswagon problem was confined to
one engine size wherein there had been a slight change of head
design that had an unforeseen negative effect on heat
dissapation.
#Post#: 2592--------------------------------------------------
Re: Banquo's Mighty Falcone top end rebuild
By: randall Date: March 21, 2019, 5:32 am
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I completely agree with what my colleagues said
and I add that to avoid malfunctions we must first get in tune
with the NFalcone, understand it, and above all love it;
The NF prefers to tide on the consular roads, possibly full of
curves, in the hills and in hours without traffic,
carefully avoiding cities and highways, so as to be able to
enjoy and listen to the rhythm of his engine, changing gear as
less as possible and avoiding high revs of the engine,
you will see ,you will never have mechanical problems and the NF
will reward you with many pleasant kilometers
;)
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