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 Setting Valve Clearances 
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viking bastard
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Joined: April 18th, 2009, 11:43 am
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Location: Meneac, Bretagne France
Post Re: Setting Valve Clearances
So all break downs are related to valve clearance :roll:

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March 3rd, 2011, 1:51 pm
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Firing on two.
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Joined: July 21st, 2010, 7:12 pm
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Post Re: Setting Valve Clearances
toomany2cvs wrote:
2CViking wrote:
Valve clearance 0.20 not 0.25 :mrgreen:


A tappy tappet is a happy tappet.


Agree, and its a nice phrase too, has a sort of rhyme to it. 0.25 for me all the time. :D

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March 3rd, 2011, 1:55 pm
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Firing on two.
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Joined: May 16th, 2010, 5:04 pm
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Post Re: Setting Valve Clearances
2CViking wrote:
So all break downs are related to valve clearance :roll:


Absolutely, get the valve clearances right and your chassis won't break, your coil and points will last indefinitely, rust is but a distant memory, your hood will be perfectly water tight, your king pins will never chatter, your battery will be charged at 14.3 volts precisely and you never need change the oil again as long as you use a Purflux oil filter. 8-)


March 3rd, 2011, 1:58 pm
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viking bastard
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Post Re: Setting Valve Clearances
Please explain why 0.25 mm is better than Citroens recommendation of 0.20 mm
Do you know what happens changing to 0.25 mm :?:

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March 3rd, 2011, 2:01 pm
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Joined: July 21st, 2010, 7:12 pm
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Post Re: Setting Valve Clearances
twofifty AZU wrote:
2CViking wrote:
So all break downs are related to valve clearance :roll:


Absolutely, get the valve clearances right and your chassis won't break, your coil and points will last indefinitely, rust is but a distant memory, your hood will be perfectly water tight, your king pins will never chatter, your battery will be charged at 14.3 volts precisely and you never need change the oil again as long as you use a Purflux oil filter. 8-)


Love it. :lol: :lol: :lol:

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March 3rd, 2011, 2:08 pm
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Post Re: Setting Valve Clearances
2CViking wrote:
Please explain why 0.25 mm is better than Citroens recommendation of 0.20 mm
Do you know what happens changing to 0.25 mm :?:


The camshaft has a base circle. You measure the clearance directly opposite the point of the cam, at the lowest spot. The base circle is ground slightly oval so that as the camshaft rotates it initially lifts the valve gently before opening the valve completely.

By increasing the valve clearance very slightly it takes fractionally longer before the follower contacts the base circle and begins to open the valve.

Therefore the valve stays closed fractionally longer which allows the head of the valve to transfer heat to the cylinder head. The head of the valve can't really shed heat when it is open. Hence the tighter the valve clearance the greater the risk of a burnt out valve.

Edit

Bear in mind that we don't have leaded fuel any more, the lead acted as a lubricant on the valve seat.

If the head of the valve gets too hot it starts to weld itself to the valve seat as the valve snaps shut. When it is opened again the weld is broken and microscopic bits of valve seat get stuck to the head of the valve. That means the valve seat starts to wear. A phonomenon known as valve seat erosion. The lead used to prevent this.

Aditionally modern fuels run hotter than the stuff we got years ago.


Last edited by twofifty AZU on March 3rd, 2011, 2:27 pm, edited 2 times in total.



March 3rd, 2011, 2:08 pm
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Post Re: Setting Valve Clearances
Anyway Cloudy, beside the controversy of 0.20 and 0.25 the pictures are excellent and should be made a sticky, if that's the right term.

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March 3rd, 2011, 2:13 pm
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Agony Aunt - You have a car problem? Speak to Ken

Joined: March 6th, 2009, 1:40 am
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Post Re: Setting Valve Clearances
Viking,
out of idle curiosity, why did this cylinder head have to be removed?
http://www.citroenclassic.org.au/Galler ... 80_jpg.htm

And why was an electronic ignition unit being fitted, instead of a replacement set of advance weights? :roll:
http://www.citroenclassic.org.au/Galler ... 85_jpg.htm

ken.


2CViking wrote:
So all break downs are related to valve clearance :roll:

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March 3rd, 2011, 2:18 pm
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viking bastard
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Location: Meneac, Bretagne France
Post Re: Setting Valve Clearances
ken wrote:
Viking,
out of idle curiosity, why did this cylinder head have to be removed?
http://www.citroenclassic.org.au/Galler ... 80_jpg.htm

And why was an electronic ignition unit being fitted, instead of a replacement set of advance weights? :roll:
http://www.citroenclassic.org.au/Galler ... 85_jpg.htm

ken.

2CViking wrote:
So all break downs are related to valve clearance :roll:


Oil feeding pipe snapped.

Push rod seal leaking badly

Ignition fitted as a test (dust and moister (creek crossings)

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March 3rd, 2011, 2:35 pm
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viking bastard
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Post Re: Setting Valve Clearances
Burning a valve or a seat is more likely to come from, worn valve guides, wrong ignition or wrong mixture than changing the valve clearance less than 0,05 mm

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March 3rd, 2011, 2:38 pm
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