How to Lap your Valves in....


These clever dicks knows how to do it

Post Fri Jan 13, 2012 6:46 pm

How to Lap your Valves in....

Though i would put this in here so later i can cut and paste it to my Supermono thread - and also it can be a bit daunting if you have never done it before.

Well Firstly what is lapping in Valves and why do it.....

When you do any work that requires the removal of your valves, generally you will de-coke them, and this will change the relationship they have to the Valve seat - not only this - but apart from having Inlet Valves in the inlet side, and exhaust Valves on the exhaust side - can you really guarentee you have put them back in the same place they came out of ???

The process of lapping them in creates the correct seal.

So firstly having De-coked your valves, get hold of some of this..... Coarse and fine GRINDING paste usually one at either end of the tin....

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Now this stuff is both a miracle and a curse - to put that into perspective this job is going to take you longer to clean than do. The reason for this is why i have put grinding in capitals and made it big.... this paste grinds, and will cause havoc in your engine if you do not clean up afterwards.

The miracle is this is probably one of the quickest jobs you will do on your engine :lmao: in fact it will probably take you longer to read this "How to...." (about 2 mins for a four valve cyclinder)

Attach a valve grinding tool to the face of your valve.... like so

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As you can see the tool is a piece of wood with suckers on each end one small one large.... for small and larger valve faces.

Gently apply a film of rough paste to the valve seat on the valve

Also apply some to the valve seat on the head

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Then insert the valve and allow it drop into its normal position. Now using the stick, try to start a fire..... boy scout style, rub the stick between the palms of your hand..... just like starting a fire..... DO NOT LIFT UP AND DOWN when grinding, every four or five turns lift the valve vertically, unseating it turn the stick slightly then drop back into the seat, recommence the rubbing. If you lift the valve up and down as you grind, you will change the position on the seat, and could possibly make an oval seat which will affect the engines performance. A tip here is as you rubbing apply GENTLE downwards pressure - your hands will slide down the stick - this ensures that the valve is seated correctly.

Literally - 10 - 15 seconds grinding, pull the stick vertically upwards and you should see this sight....


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If you look at the valve seat nearest to the camera, you can see a line of gray on the seat - this has just been ground by you......

The valve will look like this

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Once cleaned up you will see this....

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on the head and this on the valve itself.... after grinding.

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The same valve - Blurry i know before grinding.

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OK now repeat the process with the fine paste... again being careful to clean it all....

Congratulations - that's it your done - you have lapped your valves in... just one other top tip......

NOW YOU NEED TO KEEP THE VALVES IN THE RIGHT PLACE - YOU'VE JUST SEALED THAT PARTICULAR VALVE TO THAT HOLE.
Last edited by LennyVFR800 on Tue Feb 07, 2012 12:49 am, edited 2 times in total.
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Post Fri Jan 13, 2012 6:48 pm

Re: How to Lap your Valves in....

:25: nice one
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