If the cylinder head has been removed from the engine due to any reason like doing a head gasket job, then it is an ideal time to do a valve job and change valve oil seals. Valve seals also need to be changed if the engine is burning / consuming oil abnormaly. Valves seal the cylinder during the compression and power strokes. With time, the valve seats get pitted with carbon deposits (especially the exhaust valve seat) and need to be ground (verb grind) to improve sealing for better compression and torque. The valve job shown here was performed on the Renault J7T petrol engine (designed and manufactured by Francaise de Mécanique).
To remove valves and old oil seals, the valve springs have to be removed. A valve spring compressor will facilitate the job but a simple steel or aluminium pipe (at least 2-3 mm thick) with a hand-held magnet can also do the job (my case). Two cut-outs have to be made in one end of the pipe to allow magnet to pass and grab the two valve keepers while you push the pipe down on the spring retainer washer. The pipe is shown here.
If the valve keepers are stubborn, tap lightly with a mallet or small hammer on the upper retainer washer of the spring and try again. The removed valve spring with its valve keepers and upper retainer washer is shown below.
The cylinder head with valve springs removed (valves still in place) is shown below.
Here is the close-up of the old valve seal fitted over the valve stem and installed on the valve guide. It can be removed with proper pliers.
Here are all the eight old valve oil seals (removed).
The new valve oil seals are shown below. These seals are not of a universal size. They are sized according to the diameter of the valve stem.
Next the valves need to be removed from the cylinder head. Engine cylinder head with valves (intake and exhaust) and spark plugs removed is shown below.
The bigger valves are intake ones and smaller ones are exhaust ones.
The shiny intake valve seat and the pitted exhaust valve seat are visible here.
Valve grinding (or lapping) compound applied to the sealing area of the valve (shown below). Take care not to put the lapping compound on the valve stem as it would wear out the valve guide during lapping.
Put some engine oil into the valve guides. Insert the valve into its guide and then place the lapping tool over it and start lapping it with both hands, lifting it up from time to time. This grinds the valve seat and valve together, making a good sealing surface. Apply a new layer of grinding compound after some time and hear for the change of tone while grinding. Do a last run without compound and if it is smooth, job is done. Credit must go to the youtube channel of Jafromobile. Watch his instructional video before doing valve job.
Valves, one lapped and other not yet.
The new valve oil seals can be pushed down with the help of a small tube. The 10mm diameter brass tube used to install the valve seals on the cylinder head. You should use a tube according to the outer diameter of your valve seals.
The new valve oil seal installed.
Once the job is finished and cylinder head installed back on the engine, you would notice that engine starts and drives better than before.
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