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Published: May 11, 2012

A basic and informative guide:

†how to 'lapp in' valves.

Lapping in valves

Head used: Peugeot 1.4 8V Diesel 106 Mardi gras.

This is just a brisk overview made from some pictures I took a while back. It might provide someone with a useful insight into how valves operate or something. Itís a very vague guide and I know Ive missed out a lot of specific details.. but have a read if you want.

The head was removed from the vehicle due to a blown head gasket.

This was the condition just after it was removed from the vehicle and stripped down. Upon removal of components it is wise to keep parts together and remember which valves went where on the head.

As you can see it is an 8 Valve head. I have marked areas of the pictures to make things more identifiable.

Blue = Waterways- The water flows through these passages to keep the head cool and the waterways continue down into the block.

Yellow = Head bolt holes- The head bolts go down through these holes to attach the head to the block.

Pink = Oil ways- The oil flows through these passages to keep the cam and valve springs lubricated during engine operation.

Here the ports on the head are visible. The larger inlet ports are at the top with the corresponding smaller exhaust ports below.

This is the face that sits onto the block. With the head gasket blown, the head reached suitable temperatures as to become warped slightly. It required to be skimmed (A thin layer of material be taken off so as to make it sit flush with the engine block again)

Pink = Exhaust ports

Blue = Inlet Ports

Yellow = Injector ports

Holes underneath are various Oil ways and waterways

Two central inlet ports

Yellow = Valve guides- This is what keeps the valves straight and guides it to its seat.

The shiny round circles are called the valve seats.

You can see the light shining in from the other side of the ports.

After dismantling, the head was sent to get skimmed


Pink = Valve seat.. roughly

Valve lapping kit:

A filthy Valve:

If the valves were to just be inserted back into the head after the skim they would not seat correctly and form a poor seal around the port.

This is where lapping comes in.

The lapping process uses two types of abrasive paste, one rougher than the other.

Valve seats prior to lapping:

A rough surface which does not seat the valve very well at all.

The valves should be inserted into the head, applying some of the rougher abrasive paste to the valve seats and to the valves where they meet the seats.

Use the suction tool to get a seal around the valve face, then place your hands around the wood and rotate it as to provide a rotating motion. (Your hands should be positioned around the wood as if you were to put your palms together normally but with the wood in the way.. or if your hands were cold and your were to rub them together.)

A very light downwards force if anything should be applied as the abrasive material will do most of the work.

Be cautious not to overlapp by applying to much pressure or lapping for too long. This will disrupt airflow and impede performance.

Be sure to lift the valve up often, rotate and continue to lapp. This ensures a good seal right the way around the valve

You will hear and feel the valve and seat meshing together as the abrasive mates the two to one another. Do this for all 8 valves.

Remove the valves and clean them, and the seats with a cloth.

Then carry out the same procedure with the fine grade abrasive paste.

You can usually tell when the faces are mated through the sound that is produced when lapping and the ease at which the valve rotates around its seat.

Again remove the valves and clean the valves and seats thoroughly removing all grit.

The valves can now be refitted.

A nicely matched valve and seat:

This valve can now be reattached to the head

Two Valves refitted to the head:

Valves push in from block side then the spring goes on, then the retainer and a spring compressor is used to compress the spring to allow the collets to go on which sit in between a little groove in the valve and the retainer. The spring compressor can now be removed and the valve is held in place by the collets.

Valves refitted block face:

Valves refitted- top face:

I cannot be held responsible for any damage caused whilst carrying out this operation. This is merely a 'how to' guide, any mistakes made are your own.

This Article is written completely by tree. Any unauthorized copying is strictly prohibited.